I had the same issue during the downgrade to 4.14.
I can confirm, that the UUID's of the ZFS filesystems changed.
I fixed the issue with editing the config file stored /etc/openmediavault/config.xml
I created a test shared folder in each file system to get the new UUID. blkid does not show the ZFS UUIDs, therefore I decided to go this way.
Search for the Tag "sharedfolder", you will find a construct like that:
<sharedfolder>
<uuid>beefbae3-4fb8-6a47-bac9-64aed8bf57f7</uuid>
<name>GOLD</name>
<comment/>
<mntentref>2fb14b0b-3961-4d9f-b6f8-52ed1f8e3c1a</mntentref>
<reldirpath>/</reldirpath>
[...]
</sharedfolder>
Search for the new shared folder and copy the mntentref value. This is the UUID of your ZFS Filesystem.
After that search for the existing old folders and replace the mntentref with the copied new value.
Safe the file, and confirm the config change in the webinterface. (I had an outstanding confirmation)
There is also a section "mntent" with all your mountpoints and the corresponding UUID's. Maybe you can get the UUID from this section without adding a new shared folder.
Good Luck!
<mntent>
<uuid>2fb14b0b-3961-4d9f-b6f8-52ed1f8e3c1a</uuid>
<fsname>data/GOLD</fsname>
<dir>/data/GOLD</dir>
<type>zfs</type>
<opts>rw,relatime,xattr,noacl</opts>
<freq>0</freq>
<passno>0</passno>
<hidden>1</hidden>
</mntent>