When modifying a nested Address Group assigned to a route policy an error is displayed "Error: Address Object is in use by a route Policy". This happens only when a Address Group which contains other Address Groups is modified and a route policy is associated.
It does not happen using a Address Group which contains only Address Objects.
Here's how to reproduce the issue:
Create 2 Address Groups, let's say Site A and Site B and add one random address object to each of them.
Now create an Address Group (let's call it Site A_B) which includes only the Site A Address Group
Create a Static Route that contains Site A_B
Now try to add Site_B to the address group Site A_B: you will get the message "Error: Address Object is in use by a route Policy"
This is currently impacting only 6.2.x releases and above.
This issue is currently being investigated by our developers. Should you encounter the same issue, please contact our Technical Support and refer to the Issue ID below.