Sites with Non-default ports not working

I'm switching from my Barracuda Load Balancer to the F5 LTM. However, when I disable the Service within the Barracuda, and enabled the F5 Virtual Service. It doesn't work. It works for a short period if I put the Source Port from Preserve to Preserve Strict. I'm not sure what's going on. The URL is using a port (8081).

Could it be that something else is listening to this port and we are having conflicts, or is something else wrong? I read that Preserve Strict should only be used for UDP connections, this is TCP, so I'm not sure why it's been helping only temporarily.