i dont think is the controls, its the animation, check for animation image points, and set them to y 0 or to max height all image points on Y ax must be the same, if the character does a double jump, then might be that your animation has image points in different places, which causes the look of a prolonged or double jump.
also you might want to disable the mouse plugin, since you already have touch object. touch object works both on mobile as for desktop, mouse does not work on mobile unless you tick the option for touch behavior, which might cause your double jump, since the action happens 2 times.
hope it helped you.
also if those are not the causes, take a look at the events for the black part, might be that the player passes half trough it, and your collision box its somehow broke, causing your character to push up a bit.