Strange blink (repo octocat)

[Chimildic]

Sometimes when click to change theme or just new page on sidebar, shows strange page for 0.5 second and then normal page. You can try on site.
What is it, how to fix?

Screenshot

[sy-records]

This seems to be caused by incompatibility between the theme and the plugin, you can exclude

[Chimildic]

There was too heavy style. Both theme light and dark were nearly the same. The blink was when switch from one to another. Including switch pages.
I extracted equal styles in base-theme.css and difference to light-theme.css and dark-theme.css. The blink gone.