Vegas Pro 21. version 300 on Windows 11 latest release. After I'd edited about the first 20 minutes of the multicamera (2-camera) show I'm working on, the video tracks suddenly disappeared from the timeline, and the Project file (veg file) also disappeared, and I had to start over on the whole project. I've gone back to Vegas Pro 20 to resume working on this project. I'll try VP21 again later at a less "risky" time; ie, when I'm not facing a deadline.
I know... never a good idea to upgrade in the middle of a project.