You are looking at the evaporator coil assembly. This indicates a problem with the defrost system. The defrost system has four main parts:
1) The defrost heater melts the frost off the evaporator fins. If the heater breaks, the frost stays put.
2) The electronic control board starts the defrost cycle and regulates how often they are triggered. If the control fails, your refrigerator can’t defrost automatically.
3) The thermistor — also called the defrost temperature sensor — senses evaporator temperature and sends signals to the electronic control board. If the thermistor senses the wrong temperature, the electronic control board won’t turn on the defrost heater.
4) The defrost bi-metal thermostat shuts off the refrigerator defrost heater if the heater gets hot enough to damage the evaporator. If the defrost bi-metal thermostat trips to shut off the defrost heater but doesn’t reset, the defrost heater won’t turn on.
See the step-by-step troubleshooting guide and video from Sears PartsDirect to determine the issue: searspartsdirect.com/diy/article/refrigerator-wont-cool-troubleshooting-video-defrost-system-problems
For parts and diagrams: searspartsdirect.com/model/5iq7nubcuk-000582/kenmore-11173025711-bottom-mount-refrigerator-parts
Other possible issues:
Door gasket: If the door gasket is torn or not creating a reliable seal, or if the freezer is not shut tightly, humid air can leak into the freezer. When this humid air passes over the cold evaporator coils, it condenses and freezes on the coils.
Evaporator drain line is obstructed and water isn’t draining.
Finally, you could have a problem with the sealed system. Call Sears Home Services at 1-800-4-MY-HOME for repair.