Samsung oven BF3ON3T11 tripping RCD

It's about 3 years old . When switched on and heating up, after about 5 mins the RCD in the consumer unit trips ( not the MCB) Strange thing is you can reset the RCD and the oven then works OK until the next time.... It's happening now every 2 or 3 days . Is this the element on it's way out or something more serious ?
RCD also covers downstairs lights and upstairs sockets but it's the oven which trips the RCD
Thanks

Disconnect the element & insulate the connectors & then try it again, if it does not trip then it seems like the element is faulty. Without a proper insulation tester there is not much else you can do yourself.