Outer shaft bent on Syma S107

Bent shaft can cause the heli vibrate and also fly unstable.
It is certain to straighten it must remove the outer shaft, the easiest way to straighten the shaft put on a flat surface, usually above the glass, turn slowly while watching the bent position, then straighten, repeat until the shaft straight.
For S107 there are actually parts of helicopters that can be directly used as the outer shaft that is tail support, you only need to move the gear and plug
More details, see also 3ch RC Helicopter Parts