Are you using any type of screen protector on your GamePad, as if you are, it is always possible that it is interfering with the Touch Screen, perhaps a part of it is stuck under the plastic housing and is acting as if you are pressing on the screen at that exact spot.
But also, since you mentioned that when you scroll down, it will "immediately goes back to the top", which almost sounds like one of the GamePad buttons may be partially stuck, so perhaps try taking a unused, dry toothbrush to gently scrub around the button to hopefully remove any dust or other foreign material that might be causing the button to stick.
But if still no luck, it is unfortunately possible that your GamePad may need some sort of repair, so probably the best thing to do is give a call to Nintendo's 1-800-255-3700 (6 am ~ 7 pm Pacific, everyday) Customer Service number, or use their webform to contact them, and one of the service representatives can determine exactly what the problem is, and if necessary, discuss repair options/costs with you, sorry.