We have a UCM6204 (on latest firmware) connected with 4 POTS lines (3 Voice, 1 Fax) with GXP1630s (latest firmware) with an issue that I can’t for the life of me figure out. Starting a few months ago, every 5-14 days we can’t receive incoming calls. Callers hear a screeching tone for as long as the call is connected. When this happens the answering extension never rings and there is no record of the call in the CDR. A reboot of the PBX fixes the problem for a seemingly random amount of time before the issue arises again.
I have tried looking in the logs to see if I can figure anything out, but I don’t have the most experience with the system and can’t find anything that sticks out. I have tried reinstalling the firmware. I thought the fax machine was causing issues so I disabled that analog trunk and unplugged the fax machine. I enabled Fail2ban and dynamic defense thinking that the problem was a security vulnerability. I have looked in the firewall logs to see if anything is being blocked that shouldn’t be. Quite frankly I am stuck.
The system has been installed for several years without issue. The issues have arisen in the last 5 months or so.