During both War and Arena gameplay, when facing a team with a Mercer, an error occurs. Three different times, in three different ways, I have seen it.
First time was in Arenas, Mercer was the final toon to beat and upon his death, he revived, attacked, died, revived, attacked, died, until time ran out.
Then in war, I faced a team with Mercer. First time through, no problem. Defeated the team. Next time I went against the same team and Mercer was not the final toon when he started the same routine only this time I was able to stop the autoplay, which also halted all gameplay. The team would not move against me and I was unable to do anything but retreat.
Tried again with a different strategy, left Mercer for last and again, gameplay halted.
I hope this is looked into