Model IKB 3650

My Liebherr integrated fridge is freezing food in the bio fresh drawers at the bottom whilst at the same time food on the top shelves is going off because it is too warm.

The digital readout of the temperature is stuck on 4 degrees and won't budge.

This has been going on for some time and we have had 2 of the 3 sensors changed but still no joy. I am not convinced the fan at the top is working.

Any advice would be greatly appreciated. Thanks is advance.

Mark