The AI hero (Serena) was attempting to attack and the game lagged (its possible my phone switched from wifi to mobile internet), then she glitched into the graveyard. From here the AI just repeatedly...

I've noticed a couple times that when the game lags in the middle of the attack animation, the attack registers many times. I once took around 15-20 damage to my hero from a 2 attack ally haha.

I...

Ran into this bug on the mobile app (version 3.71) and am able to reproduce it following your steps! Great detective work haha

The game does seem to run into a few bugs if there is lag alright...