If one uses the forum search feature (magnifying glass icon upper right) they will find past discussion on how to roll back the firmware on the single bay My Cloud units. And one would also find the following thread (using the forum search feature) which lists links to past firmwares for the single bay My Cloud units.
https://community.wd.com/t/wd-my-cloud-v3-x-v4-x-and-v2-x-firmware-versions-download-links/148533
