HI All,
I faced this very same issue after copyback from production. I checked in RSA1 (Tools -> Assign Src system ID..) and all the systems were already assigned the IDs.
In the details tab of Monitor window I saw that the error occurred during Processing so I activated the Transfer structure and then repeated the failed step. I went smooth then.
You may like to try that and like this post if it works. 
Thanks
Mohit