Freezer Coil Not Getting Cold - Kenmore 596.58692890

Freezer Coil Not Getting Cold - Kenmore 596.58692890 We have an older Kenmore side by side refrigerator. Recently the freezer cooling was sporadic and it would sometimes be very cold, other times ice cream would be liquid, etc. My daughter noticed at one point that the defroster element was getting cherry red through the vent holes. During this period of odd behavior, the fridge was actually getting colder, enough to cause ice crystals in the milk.