Whirlpool Refrigerator freezes the drain tube

The cooling coils are designed to melt the accumulated ice and it is supposed to drain down a tube at the back of the freezer compartment and run down that tube to a tray in the bottom. Over some weeks or months, this area becomes frozen and the water won't drain. The tube is frozen solid and I have to totally defrost and wait until it thaws. Is there any fix--short of buying a new, better designed refrigerator?

There are also defrosting coils both the cooling coils and some drain systems. Check your electrical schematic with your refrigerator to check these out. You will need a DMM or VOM meter to check out these defrost coils.
You didn't mention the age of the refrigerator but the older ones used a defrost timer that was included in the defrost circuit. The newer ones have some kind of logic circuit board for defrost.

Do your testing safely.