"Get-ADGroupMember: An operations error occurred" with cross-forest members
Any group that contains a user account that is cross-forest to the group object is hitting the non-descriptive error in the title when running Get-ADGroupMember. I can successfully run the command with on groups where all members are in the same forest as the group object.
The current workaround is to use Get-ADGroup and expand the Members property and then make a subsequent Get-ADObject call for each member. This takes about 5x longer to run.
Russell Roefer commented
I had to write my own functions for this as well. The error appears to stem from Foreign Service Principals that don’t exist anymore. Cleaning those up help, but I agree that the Get-ADGroupMember should handle this.