FS-4684 this should help the proxy situation

src/switch_rtp.c

@@ -4521,7 +4521,8 @@ SWITCH_DECLARE(int) switch_rtp_write_frame(switch_rtp_t *rtp_session, switch_fra
 		send_msg = frame->packet;
 
 		if (!switch_test_flag(rtp_session, SWITCH_RTP_FLAG_UDPTL) && !switch_test_flag(frame, SFF_UDPTL_PACKET)) {
-			if (switch_test_flag(rtp_session, SWITCH_RTP_FLAG_VIDEO)) {
+
+			if (switch_test_flag(rtp_session, SWITCH_RTP_FLAG_VIDEO) && rtp_session->payload > 0) {
 				send_msg->header.pt = rtp_session->payload;
 			}