Re: apm6855-1
On the APM6855-1 it is more likely a fan fault as it has the newer round probe fitted.
On the APM6855-0 it had a flat probe ( no frost evaporator sensor ) and was a common fault.
The sensor and the fan are fitted behind the rear panel in the freezer.
The fan stops when you open the fridge door and on the early APM6855-1 also stops when you open the freezer door.
You can operate the door sensors with a magnet to test the fan.
Bob