Thank you for the response - I didn't cast him game 1 but played Emrakul in game 2 via Aetherworks Marvel, opponent resolved spell and effect on cast. It went to opponent's turn (under my control), then while I was looking through his cards and devising my sabotage of his board, he conceded. I had maybe 20 seconds of control at that point. Immediately after conceding, game did not transition to sideboard screen and was stuck on the battlefield as if the game hadn't ended yet. 2 minutes or so goes by and I got an orange fuse, and when the fuse expired I lost the match. Honestly I just laughed since it was kind of funny but definitely still should be fixed, I was able to use his ability in a later game as well without any issues but opponent didn't concede that time.
Great description, thanks so much! That will really help us try to narrow down what went wrong here.