I’ve had a similar issue removing and adding subvolumes (shares) in the past:
It sounds like you may have the immutable flag set on the pool.
From a shell, could you please try:
lsattr /mnt2
You should receive a list like (with your own shares and pools obviously):
---------------- /mnt2/rockstor_rockstor
---------------- /mnt2/home
---------------- /mnt2/root
---------------- /mnt2/tempraid
---------------- /mnt2/rockon
---------------- /mnt2/cfgCouchPotato
---------------- /mnt2/cfgDeluge
---------------- /mnt2/cfgNZBGet
---------------- /mnt2/cfgPlex
---------------- /mnt2/cfgSonarr
---------------- /mnt2/downloads
---------------- /mnt2/media
---------------- /mnt2/cfgPiHole
---------------- /mnt2/cfgPhlex
If any share or pool is displayed as:
----i----------- /mnt2/tempraid
You should be able to rectify it with
chattr -i /mnt2/<pool_or_share_name>
Please advise if this doesn’t work.