TMO inbound WiFi calling - no ringback to caller

[mdobin]

My wife has a G5s Plus. I have a G5 Plus. When the G5s is attached to Wifi and wifi calling is active, the caller does not receive a ringback. If she answers the phone, it cuts off the first second or two, like the "hello" when answering. If she is on cell only, this behavior does not occur. Regular ring back and no delay in the initial audio.

I do not have the same problem with my G5 plus.

any ideas?