Exchange 2010 SP2 Upgrade Failed (Couldn't resolve the user or group Discovery Management)

I’ve upgraded my Exchange 2010 SP1 environment (1x CAS/HUB & 2x DAG member) to Exchange 2010 SP2 according to Upgrade Exchange 2010 to Exchange 2010 SP1 or Exchange 2010 SP2

1.       CAS/HUB Server: success

2.       Mailbox Server 1: success
3.       Mailbox Server 2: Mailbox Role Failed. I’ve rebooted the server and tried restarting Exchange 2010 SP2 setup which resulted in the same error:

Exchange 2010 SP2 Setup failed with error:

Couldn't resolve the user or group "AD-domain/Microsoft Exchange Security Groups/Discovery Management." If the user or group is a foreign forest principal, you must have either a two-way trust or an outgoing trust.
The trust relationship between the primary domain and the trusted domain failed.

 Solution:

1.       Disable Discovery Search Mailbox
2.       Enable Discovery Search Mailbox:

• Enable-Mailbox discoverysearch* -Discovery
• Give user(s) Full Access Permission on Discovery Search Mailbox

3.       Upgrade Mailbox Server 2 to Exchange 2010 SP2: success

Martijn