The leaking problem is being caused by ice forming in the plastic duct that carries cold air from the freezer to the fridge compartment. When the unit kicks into defrost mode this ice melts and drips into the fridge. I know this because I too the duct out and there was ice inside of it. When I removed the duct, there was still air flow, it was not entirely clogged.
Let me stress that this problem is NOT caused by ice forming in the drain pipe from the freezer to the collection/evaporation pan at the bottom.
The duct is formed by the sheet metal panel that comprises the back wall of the freezer and a shallow curved plastic piece. I tried putting some closed cell plastic foam sheeting between the evaporator coils and the sheet metal back wall, hoping to drop the temperature of that portion of the sheet metal that forms the duct, but this did not help. I can only guess that moist air is getting into the refrigerator. Or possibly that the unit is designed to drain water that melts inside the freezer to fridge duct and that system is clogged. The fridge belongs to a neighbor that I am trying to help out. I would like to go back armed with some possible solutions, but there is not much available on the net for this specific unit, so I brought the problem here, hoping to tap the experience of some readers.