Hello.
In my case, the error appeared after adding two new drives, and creating a new zfs pool.
I was able to view the old pool and the new pool in the gui, but the reference with the shared folders broke.
Even rebooting multiple times didnt resolved at first.
Then I got inspiration from 5oundless post.
I edited the file: /etc/openmediavault/config.xml
I copied the <uuid> value from the <mntent> tag to the corresponding shared element
From:
<mntent>
...
<uuid>xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx</uuid>
...
</mntent>
to:
<sharedfolder>
...
<mntentref>xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx</mntentref>
...
</sharedfolder>
then reboot.
That resolved the error and my broken references 