This issue might occur on ProxySG appliances running SGOS version 5.x. To resolve this issue, you must upgrade to version SGOS 6.x (6.1 or above), which includes the new tcp_ip load balance feature.
Use the following CLI command on the ProxySG, This command instructs the routing algorithm to use the source IP, destination IP or both as a hash value on the outbound route.
#(config) tcp-ip routing-algorithm hashing [both | destination-address | source-address]
The default setting for the tcp-ip routing-algorithm option is weighted-round-robin and is is appropriate for all deployments (except where noted as in the examples above):
#(config) tcp-ip routing-algorithm weighted-round-robin
For details on the TCP IP Load Balance feature refer to the online manual at: https://bto.bluecoat.com/doc/14782