if you have a secondary VGA card try launching the game with right click > select graphics processor, and selecting the stronger one.
Two main problems with that: I do not have a secondary vga card, and I do not use windows. This is the one and only renpy game, I cannot play under linux. I do not have prolems even with lap rats 2, which is the most heavily graphic intensive renpy game on this site afaik.
Beeing a developer myself, I suspected some programming error(improper or nonexistent image caching, improper use of lists or other), opened the rpa, but the source is hidden. I have no problem with hiding the source, but the fact remains: the game has become unplayable for me.