Zanussi WJS1465W DOOR LOCKING?

This M/C is stored in the garage and only used occasionally. When pluged back in, to be used, the door locks and it can not be opened. It has sorted its self, after a few hours waiting, on a couple of occasion but now it seems to be stuck. Is this likely to be a fault in the door switch? if not what could the problem be and how can i fix it?