I have always had auto-loot problems, since before 6.02. Its also not a Jamba problem, does the same with no addons loaded.

If your toons are some distance away and you interact with click-to-move then they all run to the mob and loot correctly. But if they are all right next to it and interact then sometimes only 1 or 2 will loot and the others will have the loot window stuck open and I have to loot manually.

I think its just when they loot at the exact same time, If there is even a slight delay it works fine. If I wanted to fix it, but it doesn't really bother me much, is I would just make a 5 step keybind where each step sends interact to a different window.