I was using FaceTime this morning, and during the call, the "Camera is being used by another application" screen appeared.
I've searched and I found https://discussions.apple.com/thread/250893855, which says "Quit all applications that are using the FaceTime camera".
But I don't have another application using the camera -- FaceTime was using it, so how did some other application steal the camera from it? If it can be stolen, how do I find out which application that was? If it can't be stolen, why did FaceTime suddenly decide, mid-call, to do this?
Note that I've also looked under Privacy / Camera; there are no applications listed as having permission to use the camera (not even FaceTime).
(iPad mini, 5th gen, iOS 13.5.1)