This seems like the same problem as I’ve been having. It looks like it is happening to a few of us, so I’m not too sure what the difference is between us & the majority of the apple silicon users here. But I’m basically doing the same as you, try clear / seriously reduce the purgeable size on my internal in order to get stems to render. It’s been quite a headache. Here are some link of others having similar (if not the same) issue as you: Engine desktop not cleaning temp files after stem processing on mac?. 'Your system has run out of application memory'