Troubleshooting sporadic deregistration

[jcaruso]

We've got a location that has 15 T26 phones.
They all are using TCP protocol instead of UDP.
The router is a SonicWall TZ 105 (I know...). I have adjusted TCP Connection Inactivity Timeout (minutes) to 60 on all firewall rules. Also UDP Timeout has been increased to 30 seconds.

We are having phones deregister sporadically. Not limited to a single phone, every phone has done it at some point. They will re-register if we let them sit. The last one that did it re-registered in exactly 15 minutes (900 seconds), which our registration timeout on the phones are set to 900 seconds so that makes sense.

The internet is not going out, because the other phones will stay on, no other devices lose connectivity, and other conversations going on don't get cut off.

I do have level 6 syslog examples and pcaps of when this happened but I would like to not post them publicly since they contain info about our site.

Is there a Yealink tech I can send them to?

Here is a scrubbed version of the syslog for those interested: http://pastebin.com/AK56QNfZ