fixating ports between client and server

hi..

we have a java APPLICATION behind an F5, which uses tcp sockets to communicate with devices beyond F5, the trouble is that we noticed that while our application uses port 12092 to send messages to a device, wireshark shows that the src port is changed in the packet to another port, so while the device is able to recieve the message, it won't use the src port written in the packet, but would always respond the a fixed port it has (i.e 12092), however since F5 change the port it won't listen to that port and has sent back an error to the device.

my questions is this, how do i make sure that F5 relays tcp requests on the same port it got them. i already checked i've already checked that "port translation" is disabled and "source port" is preserve