Part of the freezer is not freezing
Check that fridge freezer is plugged into the mains and switched on.
If the fridge freezer has been turned off at the mains, the food in the freezer will defrost.
Check the freezer door seals are clean and not damaged.
Also check that there is nothing stopping the door from closing properly.
Check to see if the ambient temperature is too low.
For more information, see the Ambient temperature setting topic.