I think the most difficult part was just figuring out how to organize so much stuff. Where things should go on the screen, what methods/variables belonged in which classes, etc. It didn't help that my laptop overheated and I wasn't able to revive it, lol.
Yeah it's a bug, I think it's something with the collisions or validation of if the foods can interact with whatever object they're dropped on. I've looked it over a few times but wasn't able to find a fix before the deadline. The clear table button can help sometimes.