Wii updating do not turn power off
I recommend refraining from opening the Gamepad as it would void your warranty, and we don't even know if that would solve the problem.
So if I don't have it, guess I have to pay for the repair.
The behavior he mentioned is exactly the same my gamepad had when that lock poped open due to an impact.
I'm not sure if his gamepad suffered some impact (he doesn't mention that at all) but it's the same things mine did. However, the part I said was loose is the large ribbon connector in the back, you can see it here: It's the black one, not the white one.
But unfortunately I don't have the receipt, so I'll get it back from Gamestop since they have it.
Also they said I could do a data transfer by giving them the serial number located in the back of the console.