I don't have a solution yet, but I have the exact same problem. Since Apple isn't likely to solve (let along acknowledge) this bug anytime soon, I'm open to anyone else here who wants to try to tackle it with me!



I know it can't be a hardware issue because I've been dealing with it all pandemic and every time there's a patch to can'talina (10.15.1 --> 10.15.2 etc) my camera starts working again, but only for a short time.



I just upgraded to 10.15.7 and like usual, it detected my camera again. I made a point of checking if the camera was detected as the very last thing I did before closing my laptop lid for the night, and also as the very first thing I did when I opened it the next morning, and sure enough, the camera wasn't detected anymore.



Now you might be thinking that it was closing/opening the lid that caused the problem, but I'm pretty sure I did that during the day after the upgrade and the camera was still recognized.



I checked for cron jobs but there are none for my user or the root user. I'm not sure what other processes would run overnight with the lid closed (I didn't think anything was supposed to be running with the lid closed...)



Anyway, in case it's useful to anyone else, I did find these suspicious logs from the 10.15.7 upgrade, especially the very last line:



/var/log/install.log:Sep 27 19:19:16 MacBook-Pro shove[727]: [src=noflags] /Volumes/Macintosh HD/System/Library/Extensions/AppleCameraInterface.kext: restored flags 0x80000 and storage class 
/var/log/install.log:Sep 27 19:19:33 MacBook-Pro OSInstaller[644]: PackageKit: Touched bundle /Volumes/Macintosh HD/System/Library/Image Capture/Devices/MassStorageCamera.app
/var/log/install.log:Sep 27 19:19:33 MacBook-Pro OSInstaller[644]: PackageKit: Touched bundle /Volumes/Macintosh HD/System/Library/Image Capture/Devices/PTPCamera.app
/var/log/install.log:Sep 27 19:19:33 MacBook-Pro OSInstaller[644]: PackageKit: Touched bundle /Volumes/Macintosh HD/System/Library/Image Capture/Devices/Type4Camera.app
/var/log/install.log:Sep 27 19:19:41 MacBook-Pro OSInstaller[644]: PackageKit: Registered bundle file:///Volumes/Macintosh%20HD/System/Library/Image%20Capture/Devices/MassStorageCamera.app/ for uid 0
/var/log/install.log:Sep 27 19:19:43 MacBook-Pro OSInstaller[644]: PackageKit: Registered bundle file:///Volumes/Macintosh%20HD/System/Library/Image%20Capture/Devices/PTPCamera.app/ for uid 0
/var/log/install.log:Sep 27 19:19:44 MacBook-Pro OSInstaller[644]: PackageKit: Registered bundle file:///Volumes/Macintosh%20HD/System/Library/Image%20Capture/Devices/Type4Camera.app/ for uid 0
/var/log/install.log:Sep 27 19:20:08 MacBook-Pro OSInstaller[644]: Considering Migration of Bundle ID "com.adobe.CameraRaw" Location "/Library/Application Support/Adobe/Plug-Ins/CC/File Formats/Camera Raw.plugin": Migrating since no bundle exists at that local path.
/var/log/install.log:Sep 27 19:20:08 MacBook-Pro OSInstaller[644]: Considering Migration of Bundle ID "com.adobe.CameraRaw" Location "/Library/Application Support/Adobe/Plug-Ins/CC/File Formats/Camera Raw.plugin": Migrating since no bundle exists at that local path.
/var/log/install.log:Sep 27 19:20:17 MacBook-Pro OSInstaller[644]: Considering Migration of Bundle ID "(null)" Location "/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/System/Library/PrivateFrameworks/CameraImagingFramework.framework": Migrating because the bundle is invalid (bundle ID or version is nil) and no local bundle exists.
/var/log/install.log:Sep 27 19:20:17 MacBook-Pro OSInstaller[644]: Considering Migration of Bundle ID "(null)" Location "/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/System/Library/PrivateFrameworks/CameraImagingFramework.framework": Migrating because the bundle is invalid (bundle ID or version is nil) and no local bundle exists.
/var/log/install.log:Sep 27 19:23:13 MacBook-Pro Unknown[620]: /Volumes/Macintosh HD/System/Library/Extensions/AppleCameraInterface.kext is not demanded by OSBundleRequired conditions.