I am just arranging to have a LT setup on the switch that these sets are connected to (system in another location). In the mean time however, i have had a developement. one of our techs at the site in question was registering a couple of new sets for me from his desk last week. he unplugged his phone, plugged the new ones in and registered them from his connection. he then plugged his phone back in.
ever since then, his phone too has been doing the same thing. reseting over the course of a night and comming back asking for PIN. if he reboots it a second time, it comes back with his extension as though nothing was wrong.