UPDATE: it's not the touch sensor. it's a shell around the handle causing the problem. cut the shell half way down and don't make it too thiccc and it will work fine.
I've decided to print a trigger extension for the smoother throttle and brake application in the racing games. Mechanically it works great. BUT it doesn't work reliably. I believe controllers have a battery saving tactic. they don't report trigger values if capacitive touch sensor on the trigger doesn't sense a finger on it first. pressing the trigger slowly with anything non-conductive results with the same missing inputs as with my 3d print. I wish there was a way to turn this off.
