iOS version always crashing on iPad mini 6 when reaching level 60+

After playing on mac via Steam over Cross Over, I now play the game on an iPad mini 6.

Every time I reach level ~60+, game starts to crash before end of the round. I can usually get a few more rounds by closing , re-opening and resuming the game. But at some point it crashes whatever I do. The only way for me to finish the game is to remove enough buildings so that the monster get to the base before it crashes, which I hope you'll agree is a very sad moment.

Does anyone alse have the same issue? And does anybody with a higher spec'ed iPad NOT have an issue? (I'm not at all trying to find a reason to upgrade my iPad, no, no)