[Users] OpenSER 1.2.1 resend of messages not matched in tm?

Hi all, I'm running openser 1.2.1 w/ tm module. In some calls, specially FAX-calls, my gateways tries T.38 first and then performs fallback to G711. This scenario makes my OpenSER resend some messages even though it has got an ACK. What happends is that the terminating PBX doesn't support T.38 and sends a "488 Not Acceptable Media" respons to my OpenSER which is relayed back to my gateway. The relay of messages looks like this: - INVITE with T.38 from GW to PBX 1. PBX sends 488 to OpenSER 2. OpenSER ACKs to PBX 3. OpenSER sends 488 to GW 4. GW ACKs to OpenSER 5. OpenSER sends 488 to GW 6. GW ACKs to OpenSER - INVITE with G711 from GW to PBX 1. PBX OK back to GW Now after the new INVITE with G711 OpenSER starts to send the 488-messages to my Gateway again, and I'm assuming it does so because it think they are not ACKed? Any idea to what goes wrong here? Br, /Tobias