UPDATE:
I sent the phone in to Nokia. Two days in transit and a week in their hands and they supposedly "repaired a mechanical issue". It is supposedly on the way back to me. Since the ONLY time it froze was when I was answering a call, I am skeptical that this really was a mechanical issue. Feels more like software. But I will wait and see what happens when it comes back.... before I sent it in I could easily reproduce the issue.
I am sorry to report that my experience with Nokia support during this issue and trying to follow up on the status was absolutely the most HORRIBLE experience I have had in YEARS. I will start a thread in the Nokia forum just to provide feedback. Basically, the people who answer the Nokia support line are hard to understand and seem to have about three canned responses to just about any question and it is almost impossible to get past them to a "supervisor". In addition, the "status" shown on the Nokia "check status" page is either erroneous or too vague to mean anything. My status was "new repair" for a while. Then it changed to "in repair" for a week. Shortly after I called to check status (a frustrating experience similar to what I am about to relate), it changed to "asset received". Never did figure that one out. Later that day it changed to "returned". Since that implied it was NOT repaired or replaced I called again to inquire. And got another absolutely incredible and frustrating runaround. To my question of "was it repaired and if so what did you do to it" I got the same halting and hesitant answer over and over..... "when you get it back there will be paperwork in it telling you what was done". I asked again and again and got the same answer. When I asked to speak to a supervisor I was put on hold..... and then the same person came back on and told me the exact same thing... "when you get it back there will be paperwork in it telling you what was done". This happened four or five times! I persisted because my first call to check status revealed that they DID have access to more informaiton than just the status page. After about the fifth time on hold only to NOT get a supervisor, I started raising my voice. Finally THE SAME GUY told me that they fixed a mechanical problem with the screen. Sheesh! Far as I know, that information was available to him from the beginning.
Note that when I called the first time to check status, I got an identical runaround with ZERO real information. When I persisted and eventually asked for a supervisor, he finally told me that after checking further, it turned out that they were "deciding whether to repair it or replace it". But getting that information took a good 10-15 minutes of frustration and persistence. The repeated answer to my question of "you have had it for a week, what are you doing with it" was "your phone is in our facility".
Coupled with the already documented issues with the WP OS itself (erratic battery life for starters), I'm here to tell ya that unless the freezing issue is actually repaired, this will be my last experience with Windows Phone and with Nokia. It has NOT been a good one. The only bright spot is that I bought the phone used and did not pay much for it. If I had signed a two year contract to get it, I would be a VERY unhappy camper right now. As it is, I have been out of contract for several years and will probably just drink the KoolAid and sign a contract for an iPhone. Near as I can tell, they work OK and are a far more mature system. I'd prefer to go back to Android but Android phone have become too big for my tastes. Even the 820 was a bit bigger than I wanted in a phone.
Paul