Apple Silicon-native build often hangs during scene load

We upgraded our project from 2019.4 to 2020.3 recently, partly to get native AS builds -- and now on my M1 Pro MBP, the game build often hangs when loading a scene. Sometimes happens at launch, when loading the main menu. Sometimes that works but at some point it will still hang -- either when loading a game scene from the main menu, or later when in a game scene and loading a saved game. Happens maybe 30-50% of the time. I have to force-quit the app.

The logs from a dev build are not informative, they just suddenly stop with no errors, nothing unusual in them. This only happens with Apple Silicon builds. (I also duplicated the project and imported it into 2021.3, and the same thing happens in AS builds from that). Intel builds do not hang, so the problem is something with the AS-native builds. But with nothing in the logs, I don't even know how to begin debugging this. Anyone have any suggestions?