If everything in the Galaxy Store, Google Play Store and phone software-update is okay you can't do anything aside from a reset of the camera settings.
If that doesn't help send an error report via the Samsung Members app on the phone where you've the problem. Hopefully they'll resolve it in a next update
In your initial post you've said "My mrs has the same problem ( S20 plus ) . ".
It means it's a software issue and not a specific product hardware problem.
Report it via the Samsung Members app via Text Chat. See what they'll reply but probably they will say "Send an Error Report"'