bosch exel 7 1200 express

Hi can any body suggest the fault on my machine? it has been taking out earth leakage trip, i have stripped door and drum seal to access and test but everything seems to check out ok, i wonder if the heater is failing under load? nothing seems to be down to earth, i will do some more tests after the week-end perhaps feed the heater independently and see if this takes out the trip, any suggestions on this particular model will be appreciated.