What’s the strangest side effect of addon conflicts you’ve ever seen and how long did it take you to figure out?

Between Classic and into Classic TBC there was a weird conflict between some addons (I forget which ones exactly but I think it required 3 specific addons to be enabled) that if I was disconnected (or closed via Alt+F4) instead of logging out my settings would have Character Specific Keybinds enabled and sometimes reset them.

Currently I’m trying to figure out why ItemRack is telling me I can’t set keybinds during combat when I wasn’t trying bind a key to a set and have no sets bound to begin with.