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So basically if you have a group, and you know how you accidentally click on another player mid mission and it opens the box to whisper etc, well I discovered if you middle click at this point, the entire UI becomes undocked and can be moved around.
Also in this video you can see the annoying flash in, flash black, cinematic fade/zoom in, wasting sooo much time.
Anyways, the UI bug is reproducible by myself and another player. Happens only in the over world or on a mission, and not in your personal realm. Did not text Sanctum.