I have the above freezer. it could be a diplomat. The problem is that it does not auto defrost. the frost builds up and eventually the fridge does not work. De frosting it clears problem until the next time.
Any ideas please
It can be a number of things but the most common problem on a APM6855 with not defrosting was the defrost sensor. Rare to get any problems other than defrost sensors or fan motors on this model.
bob