Hello. I've figured out how to make the new SF Symbols (V3) Beta crash consistently. This crash makes the custom symbols functionality of the app inaccessible. All you need to do is drop a certain custom SF Symbol template into the app and it will start crashing. I've filed a feedback with the file attached and instructions to reproduce (FB9217085).
I'm posting here to hopefully increase the odds of this being addressed in a timely fashion as I'm trying to add support for V3 SF Symbols to my app.