My Logitech Momo FFB (black) has been crapping out in the past few days. Sometimes when I push the knob forward to downshift once, I get two downshifts instead. This is particularly frustrating when I'm in 3rd, intending to engage 2nd for a slow corner, and instead getting 1st and instantly spinning.

Is there any setting in LFS which may fix this? Perhaps a delay between button presses which I can set manually? I looked in Options > Controls but didn't see anything which sounded like this.

Gearshift Debounce does this PERFECTLY - its in Options>Misc

Ah, gotcha. It's currently set at 40ms, I suppose I should raise it? Guidelines on a possible sweet spot? What will happen if I set it too high?

Two ways for me: first, trial and error. Just set it higher and do a few laps to test if it works as it should for you.
Second: how much time, to the best of your ability, would be needed to perform two consecutive gearshifts?
I don't think I could do two consecutive shifts in less than 200 ms (well, actually more than that), so I'd use a 100 ms time as a start.

If you set it too high it would recognise a single gear shift in the amount of time specified.

Quote from Lateralus :

Ah, gotcha. It's currently set at 40ms, I suppose I should raise it? Guidelines on a possible sweet spot? What will happen if I set it too high?

I had the same problem. My debounce is set at 90 ms.

Cool, thanks.