Why is this function distorting my Bezier Curve | Bevy | Page 1

So this is the code I'm using to translate my curve. Each curve has a start, end and 2 control points. If I move them all by the same vector, logically there should be no distortion however the image shows what happens when i use this function for one curve (both are identical before). What should happen is the first simply moves by vector but clearly I don't entirely understand the math here or something

        self.startpoint     += vector;
        self.controlpoint   += vector;
        self.controlpoint2  += vector;
        self.endpoint       += vector;
    }```

#Why is this function distorting my Bezier Curve