Extra audio at the beginning of an outside call

FreePBXdistro version 2.11 .

I have a customer that has 25 YealinkT26 V7 phones behind a Freepbx system version 2.11. They are using a Grandstream GXW4108 for the phone lines. Occasionally on an outbound call we get what appears to be two touchtones playing simultaneously for the first 4 -6 seconds of the call when it is being connected. I have run TCPdump on the Freepbx, don’t hear it there. I ran the Pcap on the Grandstream, not there. I have run the Pcap capture on the T26 and it isn’t there, although there were some RTP packets out of sequence. (6%). I enabled the jitter buffer in freepbx (200ms), but alas it is still there. I say it isn’t there meaning I do not hear the noise when I playback the audio through Wireshark. I also have this issue at another location , the only difference is that the phones are Aastra 6731 phones. Both locations are using phone lines from the Cable company.

Has anyone got any clue what might be going on here?

Thanks for any ideas!