This LUA error shows up for Version 6.0.15, upon entering combat, but only once per reload.

[ADDON_ACTION_BLOCKED] AddOn 'SpartanUI' tried to call the protected function 'SUI_UF_target:SetFrameLevel()'.
[string "@!BugGrabber\BugGrabber.lua"]:519: in function <!BugGrabber\BugGrabber.lua:519>
[string "=[C]"]: in function SetFrameLevel' [string "@SpartanUI\Themes\Classic\Style.lua"]:183: in function UnitFrameCallback'
[string "@SpartanUI\modules\UnitFrames\SpawnFrames.lua"]:601: in function <SpartanUI\modules\UnitFrames\SpawnFrames.lua:594>
[string "=(tail call)"]: ?
[string "=(tail call)"]: ?
[string "@SpartanUI\libs\oUF\ouf.lua"]:226: in function <SpartanUI\libs\oUF\ouf.lua:207>
[string "=(tail call)"]: ?
[string "=[C]"]: in function `Show'
[string "@FrameXML\SecureStateDriver.lua"]:83: in function <FrameXML\SecureStateDriver.lua:73>
[string "@FrameXML\SecureStateDriver.lua"]:137: in function <FrameXML\SecureStateDriver.lua:119>