1x [ADDON_ACTION_FORBIDDEN] AddOn 'AngrierWorldQuests' tried to call the protected function 'UNKNOWN()'.
[string "@!BugGrabber/BugGrabber.lua"]:480: in function <!BugGrabber/BugGrabber.lua:480>
[string "=[C]"]: ?
[string "=[C]"]: in function UseAction' [string "@FrameXML/SecureTemplates.lua"]:364: in function handler'
[string "@FrameXML/SecureTemplates.lua"]:690: in function <FrameXML/SecureTemplates.lua:672>
[string "@FrameXML/SecureTemplates.lua"]:704: in function <FrameXML/SecureTemplates.lua:697>
[string "@FrameXML/SecureTemplates.lua"]:746: in function SecureActionButton_OnClick' [string "@FrameXML/ActionButton.lua"]:109: in function TryUseActionButton'
[string "@FrameXML/MultiActionBars.lua"]:14: in function `MultiActionButtonDown'
[string "MULTIACTIONBAR1BUTTON5"]:2: in function <[string "MULTIACTIONBAR1BUTTON5"]:1>

Thanks :)

This error is caused by something else tainting the UI, which then causes this (and other addons) to fail when they use it.
The problem with that is, whatever breaks the UI does not cause an error right then and there, but only when something else runs into it, will it fail, pointing to that addon as the cause of the problem.

If you want, you can see this one, which is the same error: #24

Thanks for this.
I was actually starting to wonder about this myself because it's happening with several different addons.
My No.1. suspect is Dominos. Just adding this here in case someone else finds this thread and could do with additional info.