We have a situation, primarily with specific numbers, where freeswitch executes a T.38 INVITE and our SIP provider is responding with a 408 Request Timeout, and Freeswitch responds with an ACK. 

However, no BYE is sent and our SIP provider thinks the call is still active, and ends up billing us for a lot of dead air.  Thankfully they have a timeout and stop billing us after 6 hours, but its still costing us a lot of money.

The error Freeswitch is giving us in the cdr for this call is: RECOVERY_ON_TIMER_EXPIRE

We've used the latest code from git as well as 1.2, and the issue persists.

Furthermore, the SIP provider claims this is not correctly following the RFC:If the response for a request within a dialog is a 481
(Call/Transaction Does Not Exist) or a 408 (Request Timeout), the UAC
SHOULD terminate the dialog. A UAC SHOULD also terminate a dialog if
no response at all is received for the request (the client
transaction would inform the TU about the timeout.)

For INVITE initiated dialogs, terminating the dialog consists of
sending a BYE.

Thanks!