Some issues I've run into lately:
1) If I play a level, reset the game, and then try to reinstall/update that same level from a knytt.bin file I get a "Could not pack file" error. If MMF has a simple way to clear file I/O (typing that made me consider deleting this entire paragraph) then this might be worth fixing, otherwise it's not hard to just close and reopen the game. Oh, and I just checked and original KS does this too, so it's probably not related to differences in how KS+ resets. Anyway… I doubt many people will encounter this error, so please don't spend much time even thinking about it.
2) I tried making a Bank 9 Object 4 override CO using a modified spritesheet ripped from KSDS (attached), but it just doesn't seem to animate properly. Am I doing something wrong, or is KS+ doing something wrong?