Main question, does anyone have a Fanvil x6s DTMF working over a sip provider ? After upgrading to latest version, 15.5 sp1 and putting several Fanvil x6s on latest supported firmware 8.8, I'm getting reports from all users and with my own testing that DTMF tones are no longer transmitting properly over the primary SIP trunk (intelepeer). DTMF (RFC2833 and In-Band) works when using a Fanvil 400 or the Windows softphone client. Neither work with the x6. I've taken some wiresharks, but can't really see why it is not working besides it just being a bug maybe? When I look at the call flow in wireshark, I see it sending DTMF tones out to 3cx from the fanvil (pbx delivers audio) and also see it sending out to SIP provider. However the other end says that the numbers being entered are not valid. So It seems like the system is getting something, just not what is being input. When I call a cell phone, I can hear the tones and they sound fine. When I look at the working phone or softphone , the wireshark call flow looks the same from what I can tell. Previously before the update to version and firmware, DTMF was working on the Fanvil x6s. I've downgraded the firmware from 8.8 to 7.5 and some in between with no success.