Surely rewiring your home is a trivial exercise as a part of troubleshooting your VoIP service... {/sarcasm}

I'm not sure what options support has to monitor individual users' devices when they have frequent reports of misbehavior (such as this), but if there's such an option you should request it. That may point out where the failure is occurring. I usually don't like to jump to the "Replace the TA" solution as an early troubleshooting plan, but maybe you would be better served with a PAP2T. Of course, you could always dig your spare PAP2T out of the closet (doesn't everybody have at least one?) and put the BYOD sip credentials on it to see if it will stay connected to the sip-byod server. I don't know how often you make international calls--outgoing int'l calls are not allowed on the BYOD server.