For some reason the rename operation is failing. Check the exact path of the file on the server. 550 errors are often given because of a non-existent file or because the file path is wrong. You also need to check that the user has the correct privileges for this path. A typing error in the file name can also lead to this error.
As you currently have a support agreement please open up a ticket on our support page which can be found here. Please upload the full debug log file (you can zip it up).