If I inspect other players and open their talent tree I get a lot of errors. This happens during combat heavily especially on moseover but also out of combat.
One one quick LFR runs I inpected a player out of combat an after a while I received this error:

7x [ADDON_ACTION_BLOCKED] AddOn 'TalentTreeTweaks' tried to call the protected function 'MultiBarBottomLeft:SetFrameStrata()'. [string "@!BugGrabber/BugGrabber.lua"]:480: in function <!BugGrabber/BugGrabber.lua:480> [string "=[C]"]: in function SetFrameStrata'
[string "@FrameXML/ActionBar.lua"]:207: in function UpdateFrameStrata' [string "@FrameXML/ActionBar.lua"]:195: in function SetShowGrid'
[string "@FrameXML/MultiActionBars.lua"]:85: in function MultiActionBar_ShowAllGrids' [string "@Blizzard_ClassTalentUI/Blizzard_ClassTalentFrameTemplate.lua"]:36: in function <..._ClassTalentUI/Blizzard_ClassTalentFrameTemplate.lua:24> [string "=[C]"]: ? [string "=[C]"]: in function Show'
[string "@TalentTreeTweaks/modules/reduceTaint.lua"]:61: in function <...faceTalentTreeTweaks/modules/reduceTaint.lua:57>
[string "=(tail call)"]: ?
[string "=[C]"]: in function ShowUIPanel' [string "@FrameXML/UIParent.lua"]:959: in function ToggleTalentFrame'
[string "@Blizzard_InspectUI/InspectPaperDollFrame.lua"]:204: in function <Blizzard_InspectUI/InspectPaperDollFrame.lua:198>`

that specific error should be resolved next update