Knock wood have no problem with my machines, anyway I ran into this site of a dutch guy who repairs early Miele PCB (Hydromatic and early Novotronic machines, e.g. W715 ).
He explains why in these models leaving the door crack open also makes PCB last longer :
http://members.home.nl/peter.stuart/miele/en/el001.html
He explains why in these models leaving the door crack open also makes PCB last longer :
http://members.home.nl/peter.stuart/miele/en/el001.html