Had this happen to me a week or two ago when I tried to watch a match while queued. Got locked in an infinite load screen, clicked "leave spectate" thinking it was the match I was watching and got hit with a temp ban. Last night Match ID 14485008 was safe to leave from someone who disconnected, I left as soon as the "safe to leave" message popped up and was hit with another temp ban for leaving. It's rough that some people are reporting getting low priority for this, even if they stay for a good 15 minutes after the message, if that's true.
Hopefully they wipe the stacking penalty if/when this gets fixed.