Screen goes black during Zoom webinar

We have a new Macbook Pro, which has an external video camera, connected through an adapter into a USB port. At random times, and not reproducible, the Video screen goes black in Zoom. The ONLY solution is to completely reboot the Mac. Leaving Zoom and reentering does not fix the problem. Does anyone have any suggestions? The Macbook is plugged into a power source, and is only running a browser and mail in addition to Zoom. The Zoom app is up to date.

We've been running webinars for years on another Macbook with the built-in camera and never had this problem. So it is either the Mac itself, the OS, or the External camera interface.

Thanks for any suggestions.