Disconnect (or crash or something)
Twice recently (I assumed the game would hold itself together enough that I shouldn't bother keeping track of when a bug showed up a second time, but it was well within a 6 hour window) I was playing a game and things stopped progressing. The animations like rain still persisted. And there no longer how long I waited, there was the time out fuse thing didn't come up.
The first time this bug showed up, after I got suspicious I quit and came back and found my turn skipped, which ruined the game (and at least one subsequent game) for me so I dropped the game.
The next time it came up, as soon as I knew something was wrong, I had no interest in playing anymore so I tried to concede on the spot, but after I opened the concession window and clicked concede, nothing happened!
Edit: I tried submitting this report with a log document and a screen recording of the concede button not working, but "Sorry, we couldn't submit your request." So I guess I'll keep those to myself.