We inherited a VoIP deployment with 30+ 908 gateways that have repetitive issues. Currently, at least once a week a gateway has ports on it that are unable to break dial tone. Our current solution is a weekly reboot of every gateway. Firmware has been updated as well as changing codecs. In house wiring has been verified.
I'm assuming that you're referring to analog FXS ports, if not please advise.
Is it possible that some of the connected devices are configured for pulse dialing? The TA908 series doesn't support it, DTMF only.
If you are still looking for an answer to this, I had the same issue on TA 924s running 12.3.4 firmware. I downgraded mine to R12.3.1.E and the issue never occurred again. At the time of downgrading, Adtran support had stated the issue was present in 12.3.4 and would be fixed in a future release to it is possibly fixed by now.
Have a client this just happened on today. 924e (3rd Gen) running version R13.2.3.E. All the configured FXS ports could not break dialtone when they started to dial. Needed to reboot to resolve.
I opened a case RQST00004992334 with support and they are investigating it further. It appears to be a bug but has not been identified fully so their dev/eng folks need more debugs prior to the 924s ending up in this state so they can write a fix into upcoming firmware revisions.