It's a combination of a radially tapered wing, too much up elevator and maybe too high a total weight and thus a higher than ideal wing loading.

And you're not alone. There's more posts around here about "bad habits" from Extras than about any other design.

The first solution is to avoid giving full elevator input for super tight loops. Second is to experiment with outboard loacted turbulators to aid in delaying the almost built in tip stalls due to the high taper ratio.

It's a fine line between weight, airfoil and stall charactaristics on such planes. We want 3D capability and to be able to do multiple snap Lomchevoks on demand but we don't want the wing tips to stall on a super slow dragged out landing approach. I got news for yaz. You can't have both. One or the other has to suffer. Folks that value the easy snaps and 3D performance have to learn to ease the model in during the landing approach with small control inputs so as not to induce a sudden and radical wing twist from the aileron motions and the typical tip stall that goes with it. With such planes you need to just "breath" on the sticks during slow flight such as landings. You also need to learn to use just the right amount of elevator input to achieve tight but stall and snap roll freel loops. Yes, it's THAT sort of design. It does not suffer folks that jam the sticks around like it's a video game.