I don't thnk there is anything wrong with the door lock. Last evening I was out with friends, I mentioned my dishwasher problem and found that a friend had the same problem on a similar machine; it would appear that this is a common problem with the Classixx range of dishwashers.. It seems that the door frame is made of plastic, it distorts in use and releases the door catch. It appears the only long term solution is to get a Bosch technician in to fit a metal plate to stop the distortion.
It turns out that this design fault is not the only one with this dishwasher, when the top basket is fully loaded the back interior wall distorts and also requires a modification.
The baseline is that this Bosch dishwasher was not fit for purpose when I bought it, it is an fact a heap of junk that will be going where junk belongs.