Tooltip for large O2 tank is stuck on screen. Persists through leaving the save right to main menu. Had just logged into the game. hit F3 and (F2 or F4, cant recall what one) at the same time when issue appeared. Suspect Mouse was hovering over O2 tank when window popped up and then vanished. pending replication. EDIT: Bug is as suspected, Caused by having the research tree be opened and then closed by another window rapidly, while mouse is in a position to highlight the tooltip of one of the research nodes. Was able to replicate the bug by repeating the F3, F4 rapid press. Can also be fixed by re-opening the research tree again. So this is a fairly minor bug. but felt it should be reported regardless.
I had one stuck on my screen even after I closed the game and had to restart my computer to get rid of it. For me it worked that way..Good luck....