I have a Kenmore Elite Upright Freezer and it works fine on the Quick Freeze mode, it freezes everything but when this process is done then it begins to defrost and by the next day food is thawing as the freezer does not maintain this frozen state. We have unplugged it for over 48 hrs and still this happens. If we continue to press Quick Freeze the freezer will stay frozen and food is fine but even turning the temp control up does not help. We have ordered a new thermostat but wanted to see if you thought this could be another problem and if so what it might be??? Thank you

The model number is 253.21041100