I have a fridge-freezer Liebherr. Fridge is not cooling well. / Freezer is working perfect. Initially the pipes that supply cold air to the fridge section were frozen, II defrosted them and it worked normal for a while. Last week I re-defrosted it manually, but the wrong intervals are now much shorter. I suspect that the heater is not working properly and therefore the pipes freeze and is not supplying cold air to the fridge