An interesting chain of events, caused a game freeze.
After a few rounds of the Carousel Gryphon cycling the creatures, I ended up with one of the Gryphon’s Springpaw creatures on my side of the battlefield.
In my hand during a previous turn, was a Shifting Scroll, that was a Duplicate spell (Secret: When a friendly minion dies put two copies of it in into your hand). I played the Duplicate, then ended my turn. The Carousel Gryphon started it’s turn. It killed the Springpaw, which triggered the Secret animation, and two Springpaw’s went to my hand, but then a card image of Shifting Scroll appeared on the left of the screen, hovering there, and the game halted. It was still the Gryphon’s turn, and the resolution of the Shifting Scroll never finished, probably because the game logic might not have a pathway to resolve a card without a cost, that was triggered as a Secret.
If you read the other posts on this forum, you will see that there are already multiple dozen reports of this happening. Whenever Shifting Scroll shifts into a secret and is then cast, the game freezes when the secret triggers.
Until Blizzard fixes it, the only thing you can do when this happens is a quick force-quit of the game, restart, and then play on after you reconnect.