[salamanderjuice]

It's been a while since I checked but if IIRC kepub is the only easy way to get the image to use the entire screen and have RTL page turns. The Kobo epub renderer does neither, and for CBZ I think you need to edit the database to get RTL page turns. Although maybe Kobo added an option for that now? Seems minor I know but it personally bothered me at least to always use kepub for them.

I'm wondering if it's a memory leak somewhere in the process since it becomes a problem as time goes on. That probably wouldn't cause the screen to wig out but maybe it's just slowed to such a crawl that touches are sufficiently delayed to look like it's wigging out? Might not be an issue on the readers with more memory and only really affects the Touch as it has less to play with.