I viewed a youtube video that spoke about a product improvement ..P-Trap drain..that eliminates warm air entering the old style non P-Trap drain. Now installed no more freezing up. One thing to note, due to age of the rubber grommet the drain goes in, it was impossible to get new drain in the correct position. I used silicone sealant at the under fridge location to seal. Worked perfect and was a perfect replacement.
Defrosting the ice took longer than the drain install !