Beko CXFG1552W – Freezer not getting to temp

Hi all

Product Code: 7295146312
Serial: 18-111281-07
I went a saw this unit today which has a customer complaint of “Freezer not at temperature”, I checked the temperature and the freezer was only at -9 but the fridge was perfect. I went through all the electrical components and as far as i could test they are fine, temperature sensors were at 34K and 26K, thermal fuses and defrost heat had continuity and the circulation fan runs when the compressor runs.
The compressor was stopped when I got there and as the unit is not iced up and the condensor on the back has a nice even temperature when the compressor is running I am reluctant to say that it is a gas issue but I am also reluctant to say that it has an electrical issue as all the components appear to work okay.
This unit only has the 2 temperature sensors, 1 is in the fridge and the other is on the evaporater in the freezer – there is no air temperature in the freezer so I am not sure how it is supposed to know that the freezer section is at temperature or if it just guesses.
I am not convinced that replacing the PCB would cure anything unless there is any modification to the programming or the option to add a freezer air temp sensor.
Does anyone know what I can do to fix it or is it just another of their poor designs?
Also any technical info or bulletins on this would be appreciated.

Thank you

Jem