Icing up behind the rear panel

I think your not able to dry out cover the insulation is saturated on cover. Any time this evaporator ices up, it damages the integrity of the insulation. I usually replace the defrost terminator and temp sensor, even though you cannot properly test it other than thru continuity. And as I mentioned, once the cover has been frozen, it should be replaced. It goes without saying that any air infiltration thru the drain line will create this environment, so consider replacing any drain tube parts at the far end which may account for this. It seems that the more humid the weather becomes during spring and summer, that these problems tend to appear. You know all to well what humidity can do if it is drawn into a sealed system. If the doors and dispenser are sealing properly, then the drain tube would be my next subject for scrutiny. Also one more thing to keep in mind is to check the defrost sensor location. On many Samsung’s, the defrost sensor was placed on the evaporator outlet. It should be located on the inlet just below the cap tube joint. You might have to remove some of the mastic glob to relocate it. I would definitely replace the cover.