We have two SIP trunks that we use. Telnyx for primary which we just ported our numbers to and Flowroute as secondary. We are having an issue where incoming external calls that are answered and then transferred to another external number causes the call to fail through Telnyx but go through fine through Flowroute. The error coming back is below: Q.850;cause=96;text="MANDATORY_IE_MISSING" Telnyx says that the invite message is missing the Contact and SDP fields. We have no issues for regular calls through Telnyx and the call connects fine through Flowroute so my question is, is there different outbound parameters for transfers versus regular calls or does anyone know why these invite messages would be missing these fields?