Most likely there is the defrost system problem.
First remove the evaporator cover (inside the freezer).
Locate the defrost thermostat and defrost heater.
Check those two parts for continuity. Remember, that the
thermostat must be ice cold.
Replace the part which has no continuity.
If both of them checks out good - replace the control board located at the rear near the compressor.
The defrost thermostat Part number: 2321799
The defrost heater Part number: 2210737
The control board Part number: W10219463
Here are the breakdown diagrams and Replacement parts for Whirlpool KSCS25INSS01 REFRIGERATOR | AppliancePartsPros.com
Thank you. Post the results.