You cannot change primary location in case a user has the databases in a MDB which they are logged into.
It means that if you have a session where you are just logged in an MDB where these databases exist, then the command will be stalled
Check if you have any process or session running where you are logged into an MDB where any of these databases exist.
I have found this proposed solution.
It worked ok.
This seems to be a little bit more complicated....I would suggest to contact Aveva Support in Paris
And please, let the Forum know what was the solution