This issue usually manifests when clicking the stick to run, and suddenly you stop running or you stop moving all together.
This fix is specific to the stick randomly cutting out in a certain position.
NOTE: You will need a soldering iron for this fix, but you won't need soldiering skills.
Step 1: How the Analog Stick Works, and What the Problem Must Be.
Your analog stick in the resting position keeps the potentiometers right in the middle or their range. This means that if you are pushing the stick forward, the potentiometer is at a high or low limit.
Because of how the stick is assembled, it can't "slip" to the middle position when it's in the forward position without the stick being completely broken. If the stick is forward, the potentiometer is turned.
The problem we're having here, is that the stick suddenly registers away from the forward position, then works when moved around again. The only way this makes sense from a troubleshooting perspective is by the controller losing contact with the potentiometer.
This actually indicates a rather common problem in electronics of a loose solder connection.
This possibility seems even more likely when you consider that you are probably pushing down pretty hard on the stick while you play.
Lucky for us, this problem is easy to fix.
Step 2: Good and Bad Solder Connections
Good soldering requires the heating of the element (in this case, the arms that stick out of the potentiometer), and the surface contact point on the board.
Fixing this issue is as easy as reheating both contact points, and letting the existing solder re-bond to both.
Soldering is a bit of a skill, but in this case, all you have to do is jab at the existing connection with a semi-fine point.
Step 3: Fix It!
2. Locate the potentiometer that rotates when you move the control stick in the direction where it has problems. Mine was the left analog stick pushed forward.
3. Locate the leads for the potentiometer. They're the three solder points directly under the potentiometer.
4. Rest the circuit board securely on a flat surface or in a vice, and heat up your soldering iron.
5. Push your heated soldering iron into the soldering joint, making sure to contact the area of the circuit board already covered by solder AND the pin that's hidden under the solder. The solder will melt almost instantly, and you'll feel your iron contact the corner made by the circuit board and the pin.
6. Count to two, and remove your iron from the solder and wait a sec for it to harden.
7. Repeat for the other two pins.
8. Make sure none of the solder from each pin leaked over to one of the other pins or other soldier points nearby.
9. Reassemble your controller, and test it out!