Flaperons also add wash-in at the wing tips in addition to slowing the plane down and causing pitch changes, which is a huge invitation to a tip stall. As a general guideline, it is best to test the effects of flaperons/spoilerons only after the engine is running well and reliably, and at a good altitude. There is a huge difference between flaps and flaperons.

In my very humble opinion, you got it down in spite of the flaperons, not because of them.

And I would not re-start an engine and take off again until I figured out what made the engine quit in the first place. Again, just MHO.