OK, thanks to some extensive internet searching, I've answered my own question, but thought I should share the information in order to help others, and to alert owners to check the spring contacts on their Norcold 1200 series fridges.
I found an on-line copy of the service manual for the Norcold 1200 series which dedicated a page to a description of the spring pins and how to service them. They supply power to a perimeter heater on the door which is meant to prevent water condensation at the door closure point.
It turns out that the spring pins on my door, all three of them, were actually stuck in the almost-compressed position. They are meant to stick out about 3/8" as this photo shows:
The pins can be pulled straight out to be cleaned and can then be reinserted. The service manual WARNS NOT TO TRY TO PRISE THE PLASTIC MOUNTING OUT OF THE DOOR as it is permanently attached. The pins must be individually pulled out.
Here's a picture of one of the pins after I pulled it out:
It was an easy job to remove the spring pins and clean them with WD40. They now move easily in and out.
I'd just like to mention as well that the "dirt" which appears to be around the plastic mounting on my fridge is NOT dirt or food. It is actually black staining of the plastic by an unknown agent. Unfortunately, the photos make it look like we have a really dirty fridge.
