We have a intergrated Zanussi Fridge/Freezer Model ZI920/9K.We have noticed an on going unpleasant smell in the frigde,unrelated to any foodstuffs.It is noticeable on opening the door but not if you smell right inside. We have tried various products on the market that claim to elimate this problem with out any sucesss.Have you any idea what could be the cause?

Bernie, January 2019