Thanks for posting. I've found an ADTRAN support ticket that matches this description. It appears the issue was specific to phones with expansion modules (sidecars), and you were going to get the firmware upgraded on the phones. Has that taken place, and if so, is the issue resolved? Any other updates to report?
Yes we did place the newest software version on our phones which did resolve our issue. It also cleared up a few others that we had.
Dubois Telephone Exchange
Cell : 307-450-8057