FTP uploads outbound through Symantec Web Gateway proceed slowly and/or stop.
"550... Overwrite permission denied" appears in either an FTP client or in a packet capture recorded during the reproduction of slow upload symptoms
SWG Appliance fails to handle TCP windowing appropriately.
Symantec reproduced this symptom in a test lab environment and will address this issue in a forthcoming build.
To workaround this behavior, Symantec recommends that you disable TCP windowing at either endpoint of the FTP conversation.
Please see the following third party documentation for steps: