Sparky gets stuck at beginning of combat
If Sparky has creatures in play that can attack after about turn 5 or 6 it will often get stuck at the beginning of combat. This error has happened in 12 out of the last 15 games I have played. At the beginning of Sparky's combat phase it starts saying "hmmm". Occasionally this results in the app crashing or Sparky conceding after 5 min or so. Most of the time it seems to continue indefiniately until I concede.
If Sparky has creatures but is unable to attack (i.e. only has defenders or all creatures have summoning sickness) then the game continues as usual.

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Sepi1337#11139 commented
I have it happen about 50% of the time in a game where Sparky has an inferior board state but one creature that could attack but will lose it to a less valuable creature it creates this loop. Like the Typhoid rats and you have a bunch of 1/1 tokens and a large board state and Sparky has multiple creatures that would all die on attack and no damage goes through. I know it's a vague setup but it appears to be looping around equitable and unequitable trades and when there is a mix of both it gets confused. A 2/1 for your 2/2 and a 1/1 deathtouch for your 1/1 free token type of deal.