I've finally managed to tie down the taint between nUI and EditMode
2 files nUI has seem to trigger the error message.
nUI_InfoPanel.CombatLog.lua
nUI_InfoPanel.BattlefieldMiniMap.lua
Both of these files reparent the Blizzard frame into an infopanel on nUI's dashboard frame.
When I have bugsack/buggrabber active I get the following error whenever I go into edit mode and entering editmode. Removing these frames from nUI's file collection the error goes away. Now, whether the issue is with the Blizzard frames being still in flux for the expansion or if there is a problem with nUI's code for the particular files I can't say as there is no trail back to a line in any file in nUI itself.
Lua Code:
["message"] = "[ADDON_ACTION_FORBIDDEN] AddOn 'nUI' tried to call the protected function 'ClearTarget()'.",
["time"] = "2022/10/15 11:56:14",
["stack"] = "[string \"@Interface/AddOns/!BugGrabber/BugGrabber.lua\"]:519: in function <Interface/AddOns/!BugGrabber/BugGrabber.lua:519>\n[string \"=[C]\"]: in function `ClearTarget'\n[string \"@Interface/FrameXML/EditModeManager.lua\"]:1479: in function `ResetTargetAndFocus'\n[string \"@Interface/FrameXML/EditModeManager.lua\"]:1514: in function `RefreshTargetAndFocus'\n[string \"@Interface/FrameXML/EditModeManager.lua\"]:1432: in function `OnEditModeEnter'\n[string \"@Interface/FrameXML/EditModeManager.lua\"]:171: in function `EnterEditMode'\n[string \"@Interface/FrameXML/EditModeManager.lua\"]:193: in function <Interface/FrameXML/EditModeManager.lua:191>\n[string \"=[C]\"]: in function `Show'\n[string \"@Interface/FrameXML/UIParent.lua\"]:2828: in function `SetUIPanel'\n[string \"@Interface/FrameXML/UIParent.lua\"]:2632: in function `ShowUIPanel'\n[string \"@Interface/FrameXML/UIParent.lua\"]:2536: in function <Interface/FrameXML/UIParent.lua:2532>\n[string \"=[C]\"]: in function `SetAttribute'\n[string \"@Interface/FrameXML/UIParent.lua\"]:3134: in function `ShowUIPanel'\n[string \"*GameMenuFrame.xml:94_OnClick\"]:2: in function <[string \"*GameMenuFrame.xml:94_OnClick\"]:1>",