I've got CUCM 18.104.22.16800-26 and 5 ATA 187
My problem is that sometimes the ATA 187 randomly deregistered and the only solution is power off and power on the ATA.
This happen to all ATA.
I've checked if there is a new ATA firmware but there isn't.
Good call... I grabbed some SDL traces from CUCM and filtered these traces by mac address of my ATA. I saw that SIP messages where coming from two different IP addresses with that same MAC address. After going through the traces and looking at when the ATA issued the "IP Address Released" status message I was able to find that they were related... After changing the port to be configured for sw access vlan <voice VLAN> and removing the switchport voice vlan command, the customer is no longer complaining about the issue and I am no longer seeing the status messages "IP addr ess released" from the phone gui.