How to reproduce 360 wired controller LT and RT buttons (potentiometer)?

Hi there.

I am building an arcade stick using a 360 wired controller (early version). I want to go 8 buttons: X, A, B, Y, RB, LB and LT and RT for 3 punches, 3 kicks function. Well, I did everything I was told and everything was going okay, but the LT and RT buttons are acting a little weird.

I have also soldered a 10K 1/4w resistor as said in this tutorial:

But, for some reason, sometimes the duplicated RT and LT buttons do not work. I need to press them 4 or 5 times to get them to work. I do not want to reproduce the potentiometer function, only ON or OFF.

Does anyone here knows what is going wrong?