every 8-12 hours your refrigerator goes into a defrost cycle to melt the ice off the evaporator coils, when this does not happen due to component failure the coil will freeze up. your unit's defrost system is controlled by a computer board called an adaptive defrost control and it has failed and will need to be replaced:
Here is the location of the control board it's listed as number 23 in the diagram below:
Here is the adaptive defrost control board kit, it comes with instructions and the new wiring harness, its an upgraded version from your original part because they had so many failures with the original so they made this kit to replace it.
Refrigerator Adaptive Defrost Control Kit
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