Upright freezer- needs repair (Brookfield, CT)

A Sears Kenmore 2012 upright freezer that was working beautifully up until about a year ago. Then the coils started frosting up and temp would start to increase. Guessing it’s either defrost timer, sensor, or heater coil; but outside my skill set to repair.
Hoping a nice opportunity for someone who knows what to do/ diagnose.
I think it’s something like 10 cu ft.
I can help you load.