Yep, Chinhglish. Here is a guess.
B and Z wheel of X use hardware debouncing. Valid signals occur when the inputs are low for at least 9.x mS. The Z-wheel debounce time is 0.8x mS.
Both the Z-axis and the Buttons are sampled every 2 uS which means the hardware can't see any state changes that occur within the 2 uS interval.
Hey, I'm used to it. What's a "plug point" and what is a "fore-ist". The former is an electrical outlet and the latter is a small wooded area