I had the same problem, after less than 5 crashes. I think the biggest problem is that the 'pins' that slot into the shock tower are slightly too small in diameter. When the thread gets damaged (which easily happens with the soft plastic*), you can move the wing from left to right on it's mounts because the pins move back and forth in their slots.
The only solutions are to create a lot of friction between the flat spots where the shock tower and wing mounts touch, aka tightening the lot together, or to remove the play/excess space in the slots.
I've put a longer screw in, and the friction is again sufficient to keep the wing from sliding from left to right (for now). I'll get some even longer screws, mount a nut on the back, and I'm going to fill up the excess space in the slots with silicon sealant, glue or something else to prevent the movement. It should be pretty bulletproof after that?
*I do like the soft plastic for it really absorbs the blows, on the chassis and perhaps even the wing a bit.