Check the Cisco Unified Communications Manager Group in your Route List. May be the Sub3 is the first priority in your CUCM Group.
Hope this helps!
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- Reset the Route List
- Do the diagnostic test from CLI and see if there is any issue.
- Create a TEST CM group with only on CM server in it and see if it gets registered with that node to which you want this to get registered with.
- Try deleting and adding it again.
- Is still there is an issue check the replication status