You have assigned a copy or move PST policy to a PST file. The .c2cpartialpst file is created in the target location, but no further data is migrated. If the PST Enterprise Copy Service is restarted on the Copy Agent, then the copy or move PST policy completes successfully. Looking in the PST Enterprise Copy Service logging you see that the affected PST reports that it is already being processed by another thread:
10 10:32:20 777299 MasterControlThread checking with service for PSTs to be processed, iteration=1
10 10:32:25 899193 MasterControlThread told of 1 PSTs
10 10:32:25 899782 MasterControlThread found pst 'c:\users\user\documents\outlook files\archive.pst' already being processed by thread slot 0
Another process has locked the PST file. This is commonly caused by anti-virus scanning.
If you have running antivirus software on the Copy Agent server, you should exclude the temporary data and target locations (as defined in the Copy Agent configuration) from being scanned temporarily to ascertain if this the process responsible. If processing proceeds as normal, then these antivirus scanning exclusions should be configured for all Copy Agent servers.