HI @rach36 Have you checked your permissions to see all is ok there/ Apps-Camera-Permissions. Are on you the latest camera update and are you able to Reset the camera,also an idea to Force stop via Apps-Camera.
If no resolution advisable to wipe the cache partition to clear temporary files, data is intact.
1. Turn off the device.
2. May need to Connect To Computer or plug in USB-C Headphones , Press and hold the Volume Up key and then press and hold the Power key
3. When the Android logo displays, release all three keys.
4. An 'Installing system update' message will show for 30 - 60 seconds before the Android system recovery menu options appear.
5. Press the Volume down key several times to highlight wipe cache partition.
6. Press Power key to select.
7. Press the Volume down key to highlight yes, them and press the Power key to select.
8. When the wipe cache partition is complete, Reboot system now is highlighted.
9. Press the Power key to restart the device.
If there are still issues check the Diagnostics to see if any errors are identified. Go to Samsung Members-Support-Diagnostics-Camera.
I do not work for Samsung or make Samsung Products but provide independent advice and valuable contributions.
My Device- S21 Ultra 5G ( SM-998B/DS ) CSC= BTU , 12GB/256GB
One Ui 5.0,Android 13 .