Something appears to be acting weirdly in campaign # 25172 - at one point during play the background color disappeared, and the GM was unable to make changes that would appear for other players (for example, adding text would show up for the GM but not for the other players despite being on the Token layer). Shortly afterward, the system interpreted any mouse movement as drawing a selection rectangle even though no mouse buttons were held down. Upon promoting another player to GM, they experienced similar issues. Problems occured on up-to-date versions of both firefox and chrome.
This appears to have started shortly after creating a large text element that resized itself off of the canvas during creation.