A YouTube video: https://www.youtube.com/watch?v=jIdtNdDXFDk , by a professional appliance repair company described replacement of the freezer drain pipe with Kenmore's (by Whirlpool) revised drain pipe. Ice buildup inside the freezer was caused by warm air beneath the freezer contacting cold air from inside the freezer the resulting condensation freezing and blocking the drain, causing the ice buildup inside. The revised drain tube functions as a p-trap to prevent cold/warm air interaction. The replacement of the original drain was straight forward after reviewing the video mentioned.