Occasionally, while engaged in combat, if I open the bag and attempt to use an item, I get the WoW on screen notification that:

"Combuctor has been blocked from an action only available to Blizzard UI. You can disable this addon and reload the UI."

The happened a couple minutes ago when I attempted to use a Halloween candy while in combat, but it has also occurred while attempting to use a mana potion. Separately, I also have the issue where in combat the "x" will not allow me to close the bag. It's not game breaking as since I'll just use the key bind.