Fault with Door Lock?

Hi.

I have a problem with our machine. The light for the door lock starts flashing and the only way to get the machine to run again is to press and hold in untill it starts runing again. This seems to happen every few minutes. I have fitted a new door lock as a fitter said that this was more than likely the problem. It is still the same. any idea's what could be causing this.

ROBERT
January 2011