Came here to say I got to the same exact conclusion. Tried creating a new character and had no issues, and when I went back on my main and left my guild, it got fixed. The issue came back after rejoining.
Other than this, nothing I’ve tried fixed it: addons, fresh WTF+Interface folders, different servers, played around with resolutions and graphics settings, tried emptying my warband, clearing my quesdtlog, removing my transmog, etc etc etc.
Only thing that works is /gquit.