Kenmore model 363.9565412 side by side. Refrigerator warm and troubleshooted to bad defrost. Replaced defrost timer, defrost thermostat and defrost heaters. Verified timer functioning and heaters coming on yet after about a month and a half noticed no cold air coming into refrigerator compartment which means an ice blockage. Manually advanced timer and could hear sizzling in freezer.......Took off access panel and there is a block of ice just above the lower heater EVEN THOUGH THIS HEATER IS ON. Manually defrosted and same thing in a little over a month. Ice above lower heating element.

I’m okay with buying all new parts again but would like to know why this might be occurring with parts that appear to be working!