There could multiple reasons why you receive an Unexpected copying error... when attempting to run Test Connection on an existing archive server.

When you run Test Connection, SPP adds a file named Safeguard_Test_Connection.txt to the Storage Path location of the archive server owned by the Account Name you entered when you created the archive server. To run Test Connection on an existing archive server with a new account name, you must first delete the existing Safeguard_Test_Connection.txt file.