Forcepoint NGFW Question with Softphones

Hello,

I am trying to get softphones on our NGFW but am running into issues where the firewall is dumping the connection because it thinks the VPN tunnel is getting spoofed. I tried to set up a SIP port range with a client VPN voice network rule but am still getting the spoofing message. Has anyone else tried this or had any luck? I really do not want to allow all ports over SIP