Moisture/water emits from the top backmost corner of my Jenn-Air side-by-side (the common wall between the freezer and the fresh food section), drips down the center wall and freezes. What part(s) are most likely to fail causing this problem? Examining the parts diagrams I find two groups of parts: one involving the airflow from the freezer side, the other from the fridge, taking the air in.

Thanks in advance