Hi,
Sorry to hear about this. Here is what I'm finding:
1. This is not Big Sur related, your crashes going back to September of 2020 (using Catalina) are identical to your recent crashes.
2. Nearly every one of your many crashes is this exact problem.
These factors indicate only a few possibilities.
1. Your design workflow introduces something. Assuming you can complete "some" sketches since September of this year, what is the difference between sketches that crash and those that don't?
2. Are you using special text objects, esp. with a unique font you installed? (not default on macOS)
Can you share one of these designs?
What happens if you turn off 3D sketching?
Phil Eichmiller
Software Engineer
Quality Assurance
Autodesk, Inc.