Video Toggling Between FaceTime camera and USB on Macbook Pro (Restarts, updates, etc don't fix)

I have been experiencing a toggling/flipping back and forth of the Video camera (the green video icon at the top of Macbook screen also glitches on/off while this happens) when using Zoom App on Macbook. When I "Start a Meeting," the dropdown in video continuously changes between "FaceTime Camera" and the "USB Camera" and nothing I have tried has solved this issue (and I can't seem to find something exactly the same happening online. ANY and all help would be most appreciated!! Thank you 🙂