Every group I sign up for then shows in duplicate - in the screenshot I am signed up for 4 groups... all show twice.

The only error I see in bugack is:

21x [ADDON_ACTION_BLOCKED] AddOn 'PremadeGroupsFilter' tried to call the protected function 'GetPlaystyleString()'.
[string "@!BugGrabber\BugGrabber.lua"]:519: in function <!BugGrabber\BugGrabber.lua:519>
[string "=[C]"]: in function GetPlaystyleString' [string "@FrameXML\LFGList.lua"]:3508: in function <FrameXML\LFGList.lua:3499> [string "=[C]"]: in function LFGListUtil_SetSearchEntryTooltip'
[string "@FrameXML\LFGList.lua"]:2576: in function <FrameXML\LFGList.lua:2573>
[string "=[C]"]: ?

I see the same behavior when applying for a group. However, groups also show up in duplicate when I disable all addons. So this issue is not related to PGF.

Regarding the error message in BugSack: this a known problem. Blizzard protected the function GetPlaystyleString(), most likely by mistake. There is nothing I can do about the error at the moment.