I don't know if this is the cause of your problem, but my freezer part of my fridge-freezer always 'knocks off' in these kind of temperatures, as it's situated in an unheated part of the house and the thermostat reacts when the outside temperature is very cold.
I don't know if this is the cause of your problem, but my freezer part of my fridge-freezer always 'knocks off' in these kind of temperatures, as it's situated in an unheated part of the house and the thermostat reacts when the outside temperature