diff --git a/VariantValidator/modules/format_converters.py b/VariantValidator/modules/format_converters.py
index d3426a5c..42d352c7 100644
--- a/VariantValidator/modules/format_converters.py
+++ b/VariantValidator/modules/format_converters.py
@@ -15,10 +15,10 @@
 logger = logging.getLogger(__name__)
 
 
-def initial_format_conversions(variant, validator, select_transcripts_dict_plus_version):
+def initial_format_conversions(variant, validator, select_transcripts_dict_plus_version, batch_list):
 
     # VCF type 1
-    toskip = vcf2hgvs_stage1(variant, validator)
+    toskip = vcf2hgvs_stage1(variant, batch_list)
     if toskip:
         return True
 
@@ -28,7 +28,7 @@ def initial_format_conversions(variant, validator, select_transcripts_dict_plus_
     if toskip:
         return True
 
-    toskip = gene_symbol_catch(variant, validator, select_transcripts_dict_plus_version)
+    toskip = gene_symbol_catch(variant, validator, select_transcripts_dict_plus_version, batch_list)
     if toskip:
         return True
 
@@ -38,13 +38,13 @@ def initial_format_conversions(variant, validator, select_transcripts_dict_plus_
         return True
 
     # Find not_sub type in input e.g. GGGG>G
-    toskip = vcf2hgvs_stage4(variant, validator)
+    toskip = vcf2hgvs_stage4(variant, batch_list)
     if toskip:
         return True
 
     # Extract variants from HGVS allele descriptions
     # http://varnomen.hgvs.org/recommendations/DNA/variant/alleles/
-    toskip = allele_parser(variant, validator, validator)
+    toskip = allele_parser(variant, validator, validator, batch_list)
     if toskip:
         return True
 
@@ -153,7 +153,7 @@ def final_hgvs_convert(variant,validator):
     return False
 
 
-def vcf2hgvs_stage1(variant, validator):
+def vcf2hgvs_stage1(variant, batch_list):
     """
     VCF2HGVS stage 1. converts chr-pos-ref-alt into chr:posRef>Alt
     The output format is a common mistake caused by inaccurate conversion of
@@ -218,8 +218,8 @@ def vcf2hgvs_stage1(variant, validator):
                           primary_assembly=variant.primary_assembly, order=variant.order)
         query_b = Variant(variant.original, quibble=input_b, warnings=variant.warnings,
                           primary_assembly=variant.primary_assembly, order=variant.order)
-        validator.batch_list.append(query_a)
-        validator.batch_list.append(query_b)
+        batch_list.append(query_a)
+        batch_list.append(query_b)
         logger.info("Submitting new variant with format %s", input_a)
         skipvar = True
     elif vcf_data[3]:
@@ -392,7 +392,7 @@ def vcf2hgvs_stage2(variant, validator):
     return skipvar
 
 
-def gene_symbol_catch(variant, validator, select_transcripts_dict_plus_version):
+def gene_symbol_catch(variant, validator, select_transcripts_dict_plus_version, batch_list):
     """
     Searches for gene symbols that have been used as reference sequence
     identifiers. Provides a sufficiently repremanding warning, but also provides
@@ -450,7 +450,7 @@ def gene_symbol_catch(variant, validator, select_transcripts_dict_plus_version):
                         query = Variant(variant.original, quibble=refreshed_description,
                                         warnings=variant.warnings, primary_assembly=variant.primary_assembly,
                                         order=variant.order)
-                        validator.batch_list.append(query)
+                        batch_list.append(query)
                         logger.info('HGVS variant nomenclature does not allow the use of a gene symbol (' +
                                     query_a_symbol + ') in place of a valid reference sequence')
                         logger.info("Submitting new variant with format %s", refreshed_description)
@@ -557,7 +557,7 @@ def refseq_catch(variant, validator, select_transcripts_dict_plus_version):
                             logger.info('NG_:c.PositionVariation descriptions should not be used unless a transcript '
                                         'reference sequence has also been provided e.g. NG_(NM_):c.PositionVariation. '
                                         'Resubmitting corrected version.')
-                            validator.batch_list.append(query)
+                            batch_list.append(query)
                             logger.info("Submitting new variant with format %s", refreshed_description)
                     else:
                         variant.warnings.append('A transcript reference sequence has not been provided e.g. '
@@ -590,7 +590,7 @@ def refseq_catch(variant, validator, select_transcripts_dict_plus_version):
     return skipvar
 
 
-def vcf2hgvs_stage4(variant, validator):
+def vcf2hgvs_stage4(variant, batch_list):
     """
     VCF2HGVS conversion step 4 has two purposes
     1. VCF is frequently inappropriately converted into HGVS like descriptions
@@ -636,7 +636,7 @@ def vcf2hgvs_stage4(variant, validator):
                         query = Variant(variant.original, quibble=refreshed_description,
                                         warnings=variant.warnings, primary_assembly=variant.primary_assembly,
                                         order=variant.order)
-                        validator.batch_list.append(query)
+                        batch_list.append(query)
                         logger.info('Multiple ALT sequences detected. Auto-submitting all possible combinations.')
                         logger.info("Submitting new variant with format %s", refreshed_description)
                     skipvar = True
@@ -952,7 +952,7 @@ def remap_intronic(hgvs_transy, hgvs_genomic, variant, validator):
     except AttributeError:
         pass
 
-def allele_parser(variant, validation, validator):
+def allele_parser(variant, validation, validator, batch_list):
     """
     HGVS allele string parsing function Occurance #1
     Takes a single HGVS allele description and separates each allele into a
@@ -1049,7 +1049,7 @@ def allele_parser(variant, validation, validator):
             for allele in alleles:
                 query = Variant(variant.original, quibble=allele, warnings=variant.warnings, write=True,
                                 primary_assembly=variant.primary_assembly, order=variant.order)
-                validation.batch_list.append(query)
+                batch_list.append(query)
                 logger.info("Submitting new variant with format %s", allele)
             variant.write = False
             return True
diff --git a/VariantValidator/modules/gapped_mapping.py b/VariantValidator/modules/gapped_mapping.py
index fd06225b..9a9b0572 100644
--- a/VariantValidator/modules/gapped_mapping.py
+++ b/VariantValidator/modules/gapped_mapping.py
@@ -8,7 +8,6 @@
 from VariantValidator.modules.hgvs_utils import hgvs_delins_parts_to_hgvs_obj, hgvs_dup_to_delins
 from VariantValidator.modules.variant import TranscriptMapData
 from VariantValidator.modules.utils import simple_dna_revcomp
-import traceback
 
 logger = logging.getLogger(__name__)
 
diff --git a/VariantValidator/modules/mappers.py b/VariantValidator/modules/mappers.py
index 1633e566..44278613 100644
--- a/VariantValidator/modules/mappers.py
+++ b/VariantValidator/modules/mappers.py
@@ -21,7 +21,7 @@ class MappersError(Exception):
 class TranscriptMappingError(Exception):
     pass
 
-def gene_to_transcripts(variant, validator, select_transcripts_dict):
+def gene_to_transcripts(variant, validator, select_transcripts_dict, batch_list):
     logger.info(f"Mapping {variant.hgvs_formatted} to transcripts")
     g_query = variant.hgvs_formatted
     # set hdp for exon mapping fetch before first use
@@ -170,7 +170,7 @@ def gene_to_transcripts(variant, validator, select_transcripts_dict):
                 query = Variant(variant.original, quibble=genomic_input, warnings=variant.warnings,
                                 primary_assembly=variant.primary_assembly, order=variant.order,
                                 selected_assembly=variant.selected_assembly)
-                validator.batch_list.append(query)
+                batch_list.append(query)
                 logger.info('Submitting new variant with format %s', genomic_input)
             else:
                 error = 'TranscriptIdentificationWarning: Mapping unavailable for RefSeqGene ' + str(variant.hgvs_formatted) + \
@@ -253,7 +253,7 @@ def gene_to_transcripts(variant, validator, select_transcripts_dict):
                             expanded_repeat=variant.expanded_repeat)
             # since we already fetched the exon mappings etc and python uses just a pointer for this set map_dat
             query.map_dat = variant.map_dat
-            validator.batch_list.append(query)
+            batch_list.append(query)
             logger.info("Submitting new variant with format %s", str(c_description))
 
         # Call next description
diff --git a/VariantValidator/modules/transcript_map_data.py b/VariantValidator/modules/transcript_map_data.py
index 7db95ce2..7ada466b 100644
--- a/VariantValidator/modules/transcript_map_data.py
+++ b/VariantValidator/modules/transcript_map_data.py
@@ -1,5 +1,6 @@
 import copy
 import logging
+import time
 
 logger = logging.getLogger(__name__)
 
@@ -141,15 +142,49 @@ def mapped_exons(self,tx_ac,alt_ac,alt_aln_method=None,hdp=None):
                     "provider (hdp) for use as a data source")
         if tx_ac not in self.exon_data:
             self.exon_data[tx_ac] = {}
+
         if alt_ac not in self.exon_data[tx_ac]:
             if alt_aln_method:
                 aln_method = alt_aln_method
             else:
-                aln_method = self.map_type(tx_ac,alt_ac)
-            self.exon_data[tx_ac][alt_ac] = cur_hdp.get_tx_exons(
-                    tx_ac,alt_ac,aln_method)
+                aln_method = self.map_type(tx_ac, alt_ac)
+
+            max_retries = 3
+            retry_delay = 0.2
+
+            for attempt in range(1, max_retries + 1):
+                try:
+                    self.exon_data[tx_ac][alt_ac] = cur_hdp.get_tx_exons(
+                        tx_ac,
+                        alt_ac,
+                        aln_method,
+                    )
+                    break
+
+                except KeyError as e:
+                    logger.warning(
+                        f"Attempt {attempt}/{max_retries}: "
+                        f"Failed get_tx_exons "
+                        f"tx_ac={tx_ac} "
+                        f"alt_ac={alt_ac} "
+                        f"aln_method={aln_method} "
+                        f"key_error={e}"
+                    )
+
+                    if attempt == max_retries:
+                        logger.exception(
+                            f"Failed get_tx_exons after {max_retries} retries "
+                            f"tx_ac={tx_ac} "
+                            f"alt_ac={alt_ac} "
+                            f"aln_method={aln_method}"
+                        )
+                        raise
+
+                    time.sleep(retry_delay)
+
         if alt_ac not in self.exon_data[tx_ac]:
             return []
+
         return self.exon_data[tx_ac][alt_ac]
 
     def tx_exons(self, tx_ac, alt_ac, alt_aln_method, hdp=None):
diff --git a/VariantValidator/modules/vvMixinCore.py b/VariantValidator/modules/vvMixinCore.py
index a68a0f1a..746f09be 100644
--- a/VariantValidator/modules/vvMixinCore.py
+++ b/VariantValidator/modules/vvMixinCore.py
@@ -123,15 +123,16 @@ def validate(self,
                 batch_queries = [batch_variant]
             if isinstance(batch_queries, int):
                 batch_queries = [str(batch_queries)]
+
             # Turn each variant into a dictionary. The dictionary will be compiled during validation
-            self.batch_list = []
+            batch_list = []
             for queries in batch_queries:
                 if isinstance(queries, int):
                     queries = str(queries)
                     queries = str(queries)
                 queries = queries.strip()
                 query = Variant(queries)
-                self.batch_list.append(query)
+                batch_list.append(query)
                 logger.info("Submitting variant with format %s", queries)
 
             # Create List to carry batch data output
@@ -151,8 +152,8 @@ def validate(self,
             flag : mitochondrial
             """
 
-            logger.debug("Batch list length " + str(len(self.batch_list)))
-            for my_variant in self.batch_list:
+            logger.debug("Batch list length " + str(len(batch_list)))
+            for my_variant in batch_list:
 
                 # Create Normalizers
                 my_variant.hn = vvhgvs.normalizer.Normalizer(self.hdp,
@@ -389,8 +390,10 @@ def validate(self,
                             my_variant.warnings.append("Reference sequence type o. should only be used for circular "
                                                        "reference sequences that are not mitochondrial. Instead use m.")
                     try:
-                        toskip = format_converters.initial_format_conversions(my_variant, self,
-                                                                              select_transcripts_dict_plus_version)
+                        toskip = format_converters.initial_format_conversions(my_variant,
+                                                                              self,
+                                                                              select_transcripts_dict_plus_version,
+                                                                              batch_list)
 
                     except vvhgvs.exceptions.HGVSError as e:
                         # import traceback
@@ -689,7 +692,7 @@ def validate(self,
                     # Now start mapping from genome to transcripts
                     if my_variant.reftype == ':g.':
                         try:
-                            toskip = mappers.gene_to_transcripts(my_variant, self, select_transcripts_dict)
+                            toskip = mappers.gene_to_transcripts(my_variant, self, select_transcripts_dict, batch_list)
                         except IndexError:
                             my_variant.output_type_flag = 'warning'
                             error = '%s cannot be validated in the context of genome build %s, ' \
@@ -737,6 +740,8 @@ def validate(self,
                         my_variant.warnings.append(error)
                         exc_type, exc_value, last_traceback = sys.exc_info()
                         logger.error(str(exc_type) + " " + str(exc_value))
+                        import traceback
+                        traceback.print_exc()
                         continue
 
             # Outside the for loop
@@ -744,7 +749,7 @@ def validate(self,
             logger.debug("End of 1st for loop - Finalising formatting")
 
             # order the rows
-            by_order = sorted(self.batch_list, key=lambda x: x.order)
+            by_order = sorted(batch_list, key=lambda x: x.order)
             for variant in by_order:
                 ###############################################################
                 # Runtime information and errors at warning and above only!!! #
diff --git a/VariantValidator/modules/vvMixinInit.py b/VariantValidator/modules/vvMixinInit.py
index c143e64f..1a53d35d 100644
--- a/VariantValidator/modules/vvMixinInit.py
+++ b/VariantValidator/modules/vvMixinInit.py
@@ -192,7 +192,6 @@ def __init__(self):
         self.selected_assembly = None
         self.select_transcripts = None
         self.alt_aln_method = None
-        self.batch_list = []
 
     # Create additional normalizers
     def create_additional_normalizers_and_mappers(self):
diff --git a/tests/test_transcript_map_data.py b/tests/test_transcript_map_data.py
index 53dd00e4..28ea30d6 100644
--- a/tests/test_transcript_map_data.py
+++ b/tests/test_transcript_map_data.py
@@ -1,5 +1,6 @@
 import pytest
 from unittest.mock import MagicMock
+from unittest.mock import patch
 
 from VariantValidator.modules.transcript_map_data import TranscriptMapData
 
@@ -246,6 +247,102 @@ def test_mapped_exons_requires_hdp():
             "NM_000001.1",
             "NC_000001.11"
         )
+
+
+@patch("VariantValidator.modules.transcript_map_data.time.sleep")
+def test_mapped_exons_keyerror_retry(mock_sleep, mock_hdp):
+    mock_hdp.get_tx_exons.side_effect = [
+        KeyError("temporary failure"),
+        KeyError("temporary failure"),
+        [
+            {"alt_strand": 1, "exon": 1},
+            {"alt_strand": 1, "exon": 2},
+        ],
+    ]
+
+    tmd = TranscriptMapData(mock_hdp)
+
+    result = tmd.mapped_exons(
+        "NM_000001.1",
+        "NC_000001.11",
+    )
+
+    assert len(result) == 2
+    assert mock_hdp.get_tx_exons.call_count == 3
+    assert mock_sleep.call_count == 2
+
+
+@patch("VariantValidator.modules.transcript_map_data.time.sleep")
+def test_mapped_exons_keyerror_retry_failure(mock_sleep, mock_hdp):
+    mock_hdp.get_tx_exons.side_effect = KeyError("permanent failure")
+
+    tmd = TranscriptMapData(mock_hdp)
+
+    with pytest.raises(KeyError):
+        tmd.mapped_exons(
+            "NM_000001.1",
+            "NC_000001.11",
+        )
+
+    assert mock_hdp.get_tx_exons.call_count == 3
+    assert mock_sleep.call_count == 2
+
+def test_mapping_options_with_explicit_hdp(mock_hdp):
+    tmd = TranscriptMapData()
+
+    result = tmd.mapping_options(
+        "NM_000001.1",
+        hdp=mock_hdp,
+    )
+
+    assert len(result) == 2
+    assert tmd.hdp is mock_hdp
+
+
+def test_mapped_exons_with_explicit_hdp(mock_hdp):
+    tmd = TranscriptMapData()
+
+    result = tmd.mapped_exons(
+        "NM_000001.1",
+        "NC_000001.11",
+        hdp=mock_hdp,
+    )
+
+    assert len(result) == 2
+    assert tmd.hdp is mock_hdp
+
+
+def test_map_type_prefers_non_blat(mock_hdp):
+    mock_hdp.get_tx_mapping_options.return_value = [
+        ["NM_000001.1", "NC_000001.11", "splign", True, 1],
+        ["NM_000001.1", "NC_000001.11", "blat", True, 1],
+    ]
+
+    tmd = TranscriptMapData(mock_hdp)
+
+    assert (
+        tmd.map_type(
+            "NM_000001.1",
+            "NC_000001.11",
+        )
+        == "splign"
+    )
+
+
+def test_is_gapped_map_cache_after_fetch(mock_hdp):
+    tmd = TranscriptMapData(mock_hdp)
+
+    tmd.is_gapped_map(
+        "NM_000001.1",
+        "NC_000001.11",
+    )
+
+    assert (
+        tmd.gap_status["NM_000001.1"]["NC_000001.11"]
+        is True
+    )
+
+
 # <LICENSE>
 # Copyright (C) 2016-2026 VariantValidator Contributors
 #