RCD just tripped after 15min with machine switched on but not working.
that suggests to me a damp-related issue, such as a drip from a leak. Sometimes condensation.
Try it with the water hoses disconnected
When it is turned off the electrically operated water valve(s) on the inlet shouls be shut. You will probably be able to see it (them) if you take the lid off.
The pump and the motor are at the bottom so I suppose water could drip on them.