you can downgrade to 5.18.xx and perform a “system only” restore on the WD Dashboard afterwards … this will restore cloud access to your device
alternatively you can leave your firmware as it is and set the timemachine share to 100% storage access, then it will work over SMB
limiting share capacity causes this bug through the SMB server software, which was resolved in SMB 4.12 … unfortunatly WD uses 4.9 in their firmware 
we had this discussion already here: Timemachine stops working after update to FW 5.19.117
