Finally got it. I use the Easy flying Mode and I found the culprit. It is the Assistance/Piloting/Assisted Take off. When ON, it throttle the power to zero on rolling on the runway. I switch it OFF and now it is going fine. I do have to set the flaps manually though. Also it seems to have remove the constant joystick throttle jittering/unresponsiveness in all flights.
There is a bug there !