LG evaporator icing

Refrigerator & Freezer Repair
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Brand:LG
Model Number:LSXS26396S/03
Main Symptom: Freezer coil freezing
What happens & when: not defrosting

Error Code (if any): F DS
Parts or tests already tried: replaced freezer temp sensor. Fan tests fine. defrost heater measures 56 ohms. defrost sensor 12k at room temp and 30k ice water. Would like to replace defrost sensor but can’t find part number for this unit.
Photos / video link:

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LG has made the defrost heater, defrost thermostat and freezer evaporator available only as an entire assembly (LG ADL73901333 Side-By-Side Refrigerator Refrigerator Evaporator Coil And Housing Assembly | Genuine OEM Part)