you could possibly try to unmount and then mount it in degraded mode using the command line, e.g.
mount -o degraded /dev/sdg /mnt2/RAIDONE
Or more complete like mentioned in this thread - probably want to match your active settings that I can see on your first post:
mount -o remount,rw,relatime,degraded,compress-zstd:3,space_cache=v2,skip_balance,subvolid=5,subvol=/ /dev/sdg /mnt2/RAIDONE
The skip_balance will just ensure that it does not try to resume a previous balance automatically …