Problem with Liebherr Fridgefreezer CTNes 3123

Dear Sir/Madam,
As of late the freezer section of my combined Liebherr fridge freezer does not seem to be operating at its maximum capacity. Whenever I place ice cream in the compartment it remains/turns soft whilst other items such as ice and meat remain frozen. The lights indicate -18 and 3. I have read on the Liebherr forum that it could be something to do with where my freezer is situated. It is situated in the kitchen where there is no radiator and during the day the house remains unheated until around 5 pm each day. They mention something about a winter mode. I have turned off a fan which is in the fridge compartment, but am not sure if that is what they are going on about. Also I do have a microwave located on top of the fridge freezer but am not sure whether this could have an impact on frozen items within the freezer compartment. I have also noticed that the rear section of the freezer has produced some frost even though it is a frost free freezer. Any input regarding whether I need to get it checked out by an engineer would be gratefully received. Thank you. Clive