The crash seems to be the interaction with Imp Shaman’s trait and a Nature-swapped Timewalk spell gem.
“When your creatures cast a single-target Nature spell, they have a 50% chance to cast the spell on all the creatures fighting on the target’s side.”
When casting timewalk- it has crashed 3 times, and not crashed 3 times. It still crashed after removing any additional enchantments from the Timewalk gem when I tried narrowing down the cause. It definitely seems to be the 50% chance that is causing it.