As per the procedure, I upgraded the Network Load Balancer first and then Mailbox Servers. Network Load Balancer upgrade went fine without any issues. Installed Update RollUp 4 as well after upgrading it to SP2. Started upgrading Member server of DAG, you can refer to this Tech Net article to upgrade DAG member servers.

Both the member server MBX02 and MCSHT got upgraded as expected, while upgrading the MBX01 it failed on stopping Microsoft Exchange RPC Client Access Service twice.
Restarted the server and upgrade completed successfully. Installed Update Rollup 4 as well on all the servers. After upgrade now it's time to move the everything back as it was before upgrade. So ran the below command:
Move-ActiveMailboxDatabase "DB01" -ActivateOnServer MBX01 and it failed with below error.


Checked the status of the server by running the command:
Get-MailboxServer MBX01 | fl Name,DatabaseCopyAutoActivationPolicy  and it says Unrestricted, hence it's not blocked. Ran the command again and it failed with the same error message. Tried from GUI and as expected, it had to failed.
Friend of mine with whom I was working with, suggested that we should try to Suspend the copy of database residing on MBX01 and resume the DatabaseCopy than try to move.





ActiveMailboxDatabase from GUI




Surprisingly it worked like a charm. It's a BUG and I checked in Update RollUp5 v2 and it hasn't got fixed yet.

Cheers,