While I ordered a replacement joystick potentiometer slider (see my post from last week), I thought that you could also simply move one slider from a less used joystick axis to the one used most (left joystick, up-down direction). Much less used is the right joystick up-down). So I open the joystick again, bent off the housing of the those and swapped the up-down potentiometer sliders of the 2 joysticks. And while it was a bit fiddly with moderate amount of force needed to open and close those plastic housings of the slider, it worked fine and it completely fixed the intermittent failures to move forward via the left joystick!
Without re-calibration there was a tiny drift up (sometimes I walked very slowly forward). After re-calibration it’s rock-solid and works perfectly.
Reminded me of Tire Rotation in a car. In 2020 you rotate potentiometer sliders instead.