Playing against Illidan in Standard mode, they tried to use Frozen Shadoweaver to freeze my Draconic Emissary. Their card and targeting showed as normal, and their mana showed as spent, but then gameplay just stopped. The card turned back to being face down and just floated in place in the middle of the arena. Their turn never timed out. I could still hover over cards (and it looked like they could too, but I don’t know if those visuals accurately reflect opponent actions). After about twenty minutes of checking in intermittently, nothing changed so I quit.