Hotpoint wml540 door lock problem??

I replaced the door interlock on the above machine last week, the fault had been that the machine would not start the program and the door lock was continuously clunking.

I have had the customer back on today reporting that over the weekend the machine has started to do the same thing again though now and again it will start a program.

Is it likely to be a dud door lock, or is there a darker evil at work here? 😆