The quickbar rearranges itself between missions.

This is less of a big deal for sandbox mode, but it is a huge deal in the campaign, where each new map shuffles my carefully arranged quickbar, and I have to take 10 minutes out of the first battle of each map fixing it.

A somewhat lesser problem exists with equipment trading. If I use my last healing potion in battle, and subsequently give a few more to that champion, they don't end up in the same spot (which is now filled by some junk).