I wonder if this is something anyone else has come across:

We make a call out to this particular customer via our wholesale SIP provider. 

Other end picks up and tries to transfer the call.
The call is dropped out end by FreeSWITCH following a reinvite from the remote end with no SDP. FreeSWITCH sends 200 with SDP, other end ACKs then FreeSWITCH drops the call "No answer to offer"

We use BT Wholesale's IPEX product and I think we can assume that this call is SIP end-to-end (this is something that I'm finding increasingly common) and what is happening is FreeSWITCH is seeing the reinvite as a late negotiation invite and when the ACK comes back with no SDP, thinks the other end has refused and hanging up the call.

I've not tested with inbound-late-negotiation disabled and am hoping to avoid doing so. I have tried setting renegotiate-codec-on-reinvite to false on the outgoing profile which has made no difference.

I'm using FreeSWITCH 1.6.19

Kind regards,