This looks like a codec renegotiation problem. Can you share detailed traces from CUCM ?

Russell, If this problem is not fixed yet, may I have detailed Call Manager service traces? It will help indicate why CUCM sends 488. This is sent because of a media negotiation problem. The traces will help. ~Avi

The problem is indeed that INVITE I posted. It is not a RE-INVITE, hence it is wrong for ISP to send that second INVITE. TThe RE INVITE will come after session is established. Here the second INVITE comes before session establishment. This is the pro...

We have our own priorities aokanlawon . :P  I took a stab at the traces, and also tried some stuff in lab. I think it is better for you to contact TAC for a detailed explanation. I couldn't infer much from the CCM SDL traces as they were provided fro...

Can I please see working debug ccsip all, debug voip ccapi inout  please? Give calling and called number too or CALL-ID. I believe this second RE-INVITE in the calling leg is wrong: 4277334: Nov 17 08:43:14.909 AEST: //-1/xxxxxxxxxxxx/SIP/Msg/ccsipD...