Yet another Action Blocked error. I received this one while having my map open and entering combat because a mob aggroed me. Thanks.

2x [ADDON_ACTION_BLOCKED] AddOn 'Mapster' tried to call the protected function 'UNKNOWN()'.
[string "@Interface/AddOns/!BugGrabber/BugGrabber.lua"]:480: in function <Interface/AddOns/!BugGrabber/BugGrabber.lua:480>
[string "=[C]"]: ?
[string "@Interface/AddOns/Mapster/Libs/LibWindow-1.1-18/LibWindow-1.1.lua"]:178: in function RestorePosition' [string "@Interface/AddOns/Mapster/Mapster.lua"]:186: in function SetPosition'
[string "@Interface/AddOns/Mapster/Mapster.lua"]:219: in function <Interface/AddOns/Mapster/Mapster.lua:216>
[string "=(tail call)"]: ?
[string "=[C]"]: in function SynchronizeDisplayState' [string "@Interface/FrameXML/QuestLogOwnerMixin.lua"]:141: in function SetDisplayState'
[string "@Interface/FrameXML/QuestLogOwnerMixin.lua"]:74: in function HandleUserActionMinimizeSelf' [string "@Interface/AddOns/Blizzard_WorldMap/Blizzard_WorldMap.lua"]:72: in function minimizedCallback'
[string "@Interface/SharedXML/SharedUIPanelTemplates.lua"]:875: in function Minimize' [string "@Interface/AddOns/Blizzard_WorldMap/Blizzard_WorldMap.lua"]:256: in function <...rface/AddOns/Blizzard_WorldMap/Blizzard_WorldMap.lua:240> [string "=[C]"]: ? [string "@Interface/AddOns/HandyNotes_Guild/libs/AceHook-3.0-9/AceHook-3.0.lua"]:95: in function <...ns/HandyNotes_Guild/libs/AceHook-3.0/AceHook-3.0.lua:87> [string "=[C]"]: in function Show'
[string "@Interface/FrameXML/UIParent.lua"]:3143: in function <Interface/FrameXML/UIParent.lua:3129>
[string "=[C]"]: in function ShowUIPanel' [string "@Interface/FrameXML/QuestLogOwnerMixin.lua"]:103: in function SetDisplayState'
[string "@Interface/FrameXML/QuestLogOwnerMixin.lua"]:41: in function HandleUserActionToggleSelf' [string "@Interface/AddOns/Blizzard_WorldMap/Blizzard_WorldMap.lua"]:439: in function ToggleWorldMap'
[string "TOGGLEWORLDMAP"]:1: in function <[string "TOGGLEWORLDMAP"]:1>

This error looks like your World Map is for some reason marked as "secure" - which by default the map is not, and if another addon turns it secure (eg. by attaching a secure button to it), then these errors will happen - this is not a supported action for Mapster.

You can check if your map is protected/secure with this command:
/dump WorldMapFrame:IsProtected()

By default, you should get "false false" as a result. If it says "true", then an addon is breaking your map in combat.