11yr old Whirlpool ARC4020 – Faulty Stat or something else?

Make: Whirlpool
Model: ARC4020 (Total Frost Free)
S/No: 850140201000
On the same label: JE3116054

About 4 months ago whenever I opened either the fridge or freezer door, the motor cut in and out rhythmically in sync with both the internal light going on and off as well as the warning ‘beep’ going on and off. This was subsequently fixed by replacing the capacitor alone that was on the 4812 218 38159 control board.

Since then I have become aware that the fridge is not getting as cold as it used to. Placing an internal thermometer probe into the fridge cavity I was able to read the temperature externally where I was getting readings of between +8C and +12C. Repeating the same exercise with the probe in the freezer section, I returned from a 3 week holiday to find the temperature at -1.3C. The icecubes weren’t even solid. Have since turned both the fridge and freezer settings to max, but even now the freezer has only reached -11C.

I still hear the motor cutting in and out and if it is operating whilst either door is opened, the motor stops, as has always been the case.

I assume there are two separate thermostats but I can’t believe they have both malfunctioned at the same time, so is there something else that isn’t working correctly that is causing this lack of cooling/freezing?

Thanks in advance.