Outgoing calls on a Grandstream producing strange tones

I have two systems. Both at ver 2.11, both up to date. I have a GXW4104 and a GXW4108 that are doing the same thing. On outgoing calls I get the 1st ring, (system generated) then before the audio is turned over to the phone system I get either two distinct DTMF tones or a 5 - 6 second tone. I have the GS FXO’s upgraded to the newest firmware. Grandstrem has not responded for almost two weeks on the ticket I entered into their system, nothing on their forum either.