update...
Thawed the fridge out, replaced the defrost heater, all sensors, new fan, modified the drain heater, modified the drain tubes...fucking fridge is freezing up again. <sigh> I guess I'm gonna have to replace it...even though it's only 5 years old. Apparently this is a well known (within the appliance repair world) Samsung refrigerator problem. This is the kind of low-quality build that kept me from buying Korean-made garbage...everyone told me, "The Korean companies have fixed their quality control problems and are now as good as...or better than any other appliance company."

It's just too bad that nowadays, most of the US brands aren't actually American made any more.
It sucks that instead of getting better and lasting longer, appliances that used to be built to last 20 years, 30 years, or more...now barely last 5 years.