Beko Drcs68w tripping the house rcd.

My mother in law has a Beco Drc68w, it was tripping the rcd on her consumer unit, ive double checked the socket and its not the coluprit.

I removed and checked and found a knackered heater unit, which I have replaced, still it trips.
Disconnected the heater, still it trips, took the thing apart to disconnect the motor, still it trips, pump, still it trips, microswitch still it trips.
Checked the ntc and that has a ohms reading, no shorts.visual inspection has found no water, I have removed so much fluff.
This is the thing it trips after 12 seconds, it takes roughly 10 to put it into service mode then bamm.

There no signs of scorching or smells, the only two thing I havnt check are the main board and wiring, wiring ive checked as much as I can.

Any ideas guys, I know tripping the rcd means a insulation fault to earth, but how do I check the mainboard apart from checking the individual, which I have the equipment for.
Help