I've had my Wii U practically since launch and at the beginning of this year I started to notice that the left analog stick on my Wii U Gamepad didn't work properly. It started with DK Tropical Freeze. Almost every time I ducked/crouched DK would rapidly crouch and then get up by himself. It was really frustrating especially in the mine kart levels. It doesn't happen with the Pro Controller. Then I noticed it with the Wind Waker: sometimes when I moved Link backwards he would either move slowly or stop completely along with some weird movements. The problem started to fade with time, but now it's back... with a vengeance 
.
Not only do both things happen almost every single time, when I try to navigate the Wii U menu with the left stick it starts moving around a lot. For example if I move it left, it will move left but then will go up (when going through the applications). 
In the eShop, if I use the left stick to go down, it does it slowly or stops and then continues. If I use the right stick it's fluid so the left one is the problem here.
I've cleaned both sticks with a toothbrush many times but it keeps happening. Also, the left stick feels more stiff than the other one.
My only solution is to send it to Nintendo but it isn't under warranty anymore 
. Anyway, I'll send it, but will I need to send the whole console or just the Gamepad? I won't have anything to play with, and I recently acquired a 2TB HDD for the darn thing.
Well, thanks for reading this. I'd really appreciate it if you answer my question and if you have any of these problems please share your experience. 