Thermador refrigerator water pooling under crisper drawer

[rpgelber1]

Hi and thanks in advance for any help you can provide.  I have a Thermador built-in refrigerator model T36IB800SP, about 7 years old, which is a single-door bottom-freezer model.  Recently, a small amount of water has been accumulating at the bottom of the refrigerator compartment, some of which eventually freezes into a thin sheet of ice.  Being somewhat of a DIYer, I opened up to top of the refrigerator compartment to check the drain hole and evaporator drain coming from the top back wall.  There wasn't any standing water at the drain hole and I snaked a soft tube down the drain and didn't feel any resistance.  Put it back together and the problem continues.  I have tried to no avail to get diagram or service info on possible clogged or frozen drain in the freezer compartment before I start taking that apart.  Would also be good to know more about the evaporator heater and potential issues there.  Ideally, I was trying t get hold of service manual.  I've repaired dishwasher, heater furnace, dryer,. oven,... once getting a little guidance.  Anyone have experience with these units?  Thanks!