Can someone give me some advice pls?

Problem: I have a user stuck with a warm fridge at home. Top shelf at least 13C and 2nd shelf from top about 9C at the maximum thermostat setting. Higher temperatures when thermostat setting is set between normal and maximum.

Investigation sofar:
Fridge engineer (on behalf of the manufacturer, Baumatic) has come 4 times, changed the fridge 2 times and the last engineer (a different one to the previous 3 visits) confirmed that it is normal to have a temperature differential of 5-6C if the fridge has no internal fan to circulate the air. That means this is a design "feature" and the fridge is not faulty.

I also know that for domestic fridges there are no laws governing the temperatures within a fridge but there are for commerical setting (max 8C).

Next steps: I am keen to try to get money back from the fridge manufacturer based on the argument of food safety despite the fridge may not be faulty.

My questions are as follows:
Is it really true that the fridge is not faulty? Is there any engineer out there who believes that the fridge is faulty?

Which.co.uk legal team suggests that I get an independent reoprt to prove Baumatic wrong before I try to get the money back because from Baumatic perspective the fridge is not faulty.

Any comments welcomed.

Many thanks, Freda