Neff U1722 Double Over Earth Tripping?

Purchased a used neff double oven that has not been used.
I turned the bottom oven on then the top oven after about 4 minuites the earth breaker tripped, I reset it turned the bottom oven on all was fine.
Turned the top oven on and it tripped again. I then only turned the top oven on and it tripped another 4 times only on the earth breaker
The earth breaker is rated 63A and the circuit breaker is rated 32 A the circuit breaker is not tripping ?

Graham Bollard
March 2013