Although it seems only a few people have issues, I wanted to put out the most common issues. The two mods that usually help people are:

And I use RX13 better repack for the chara studio version. Updated with the kkmanager tool.

These are the most common fixes for scenes. Hope it helps!

Sadly, there are many versions of Koikatsu out there that are highly modified now so

If you are still having issues, there is a technical help server on the koikatsu discord server here: https://discord.gg/63J6yvre