RTP Audio Stalled

[WU6X]

I'm getting a condition when connecting to a remote setup where the display lights, but no audio comes through. This is intermittant; sometimes it works fine. The STATUS page of the RRC shows, Connection status: "Faulty", SIP Status: "connected and transferring", RTP/UDP audio status: "Stalled (12)". Audio Quality is matched on both ends.

Radio: TS-480HX; RRC-1258 MkII; CAT cable connection to router; all ports forwarded properly on radio end. The local LAN connection works flawlessly, all ports forwarded and firewalls off. But profile for remote connection has the problem

Any ideas on where to look from here would be helpful.

[WU6X]

I thought to repost on this issue for others having a similar problem, as I found the solution. Per the manual, page 240, SIP ALG must be disabled in the router. On this new installation, the router was furnished by the ISP and I forgot to tell them to DISABLE SIP ALG in the router ... and, that was the problem. All is working perfectly now.
Dennis - WU6X