You most likely have either a bad defrost timer or one of the thermostats are bad! None of these was even mentioned but will cause the issue that you are experiencing!
Your refrigerator has a defrost timer. It can be found behind the refrigerator's lower kickplate, in the refrigerator's control panel, or on the back wall. Four metallic terminals extend from the bottom of the defrost timer. Once you have found it, remove the timer.
Here is the video for replacing the thermosts (Both Fridge, and Freezer);
https://www.youtube.com/watch?v=kQ4YOjGq6MQ
The heater coil you said was replaced.
Here is the video for replacing the heater coil (Just in case)
https://www.youtube.com/watch?v=bPJM0TCaQDg