Hi @DannyG88. re there any updates pending on your phone? Head into Settings > Software update > Download and install to see.
Is there any damage to your camera lens?
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
Many people doesn't seem to know this. So in total for updates for your phone you always need to check in 3 places. You're welcome
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"'