A very common issue with frost free refrigerators especially in the summer months is ice build up or frost in the freezer section, normally on the back panel. Frost free refrigerators are not suppose to have ice or frost build up. This is typically caused by something in the automatic defrost cycle not working such as a defrost timer, a control board, a defrost thermostat or (Bi-Metal) or the defrost heater. In this post, I will explain how to diagnose a failed heater.
Quartz defrost heaters are simply made up by having a element that produces radiant heat triggered by the refrigerator's auto defrost cycle. In many cases you can simply inspect the heater for black or burnt spots on the glass tubing such as this #61001846 defrost heater https://www.appliancezone.com/61001846-whirlpool-refrigerator-defrost-heater/
You can also use a multi-meter to check for continuity on the heater to ensure it does have continuity .. a meter such as this one can be used to perform the check https://www.appliancezone.net/ms8233d-crenova-auto-ranging-digital-multimeter-tool/
If there is no continuity then your heater is bad and will need to be replaced. Be sure to handle new heater carefully.. try not to touch the glass part of the heater as salt and oil from the skin can shorten the defrost heater's life-span.