Now that is a guide!!! Thank you
That is quite the guide! I'll point out that at step 5.3.1 the rectangular thingy at the top (the potentiometer) just pulls out without needing to pry out the custom plastic Thrustmaster bit it's pushed into, although doing that looks necessary to fit the Hall sensor....
When I pulled out my original potentiometer it had a oily coating on it and in it. This oily stuff wasn't on the replacement potentiometer I purchased. My theory is that whatever this oily stuff is softened the carbon track in the potentiometer and it was scraped off during normal use. The new one without the oily stuff has worked perfectly ever I installed it. The only source for the oily stuff I can think of is the lubrication Thrustmaster put on the ball of the joystick. Perhaps some joysticks are stored or shipped upside-down and the lubrication drains down the shaft into the potentiometer?
In any case, that's two options: replacement pot or Hall Sensor. IMO, just replacing the potentiometer is cheapest and simplest. You can also have a look at the imgur link in my signature for a more complex modification with two 5-way switches.