T38 reinvite - not forwarding the T38 RTP

Please see the attached wireshark graph

My switch starts the call in g711.   The receiving fax device realizes it's a fax and negotiates T38.   The t38-gw starts to send t38 type packets, but the SBC never forwards them on (at 150.534 in the graph) 

The problem I see is that the SBC-in interface hasn't received the 200-OK yet (at 150.629).

The port #s remain unchanged (ie...the RTP up in 149.534 is using ports 11586/30116 for g711u).    The T38 comes in on the same port pair, but with a different codec.   

I don't know if the SBC looks at the payload to see if it matches the types he's expecting before he forwards....or if the t38 messages are processed by the SBC...and thus ignored because the signaling hadn't finished setting up for t38.