If the evaporator coils behind the back panel of the freezer are icing up because of auto defrost failure that will stop the circulation of cold air and eventually affect the freezer too.
check defrost heater, defrost thermostat. Refrigerator Repair Guide: How To Fix a Refrigerator - ACME HOW TO.com
If the heater and thermostat are ok itíll be the control.
Part 801 on diagram 10. Replacement parts for GE PSH23SGPABS | AppliancePartsPros.com