How can I fix my Smeg DWI 409C Dishwasher?

Machine will sometimes work fine and completes cycle. Other times it is difficult to obtain a solid red light using the button program selector on control panel, before closing door to start. Even when you have the solid red light and close the door, the machine just gives a couple of beeps but does not start. Sometimes the machine stops mid cycle and there is water in the machine. When the machine does start it seems very noisy (strong Brrrrr ) for a while. The door interlock and micro switch have been changed. Would like to narrow the field with parts to change if I could. Thanks. Paul