In other hand, my SFS potentiometers are ok. Actually one of them are pretty good. The another is having some spikes. But, no problem, because I use to fly with one of the axis to control two turbines aircrafts. My luck is that I found - in a small eletronic commerce in my city - two potentiometers with exactly the same physical specs of the SFS potentiometers. I bought two as spare parts for the future. They are 10k (original is 100k), but, no problem, because is in the range of the MMJoy2 and the ProMicro Arduino.