On Xorg, Leopold FC210TP Asynchronous numpad is problematic with numlock turned on.
 

Leopold FC210TP's numlock is asynchronous and independent from other keyboards' numlocks.

With numlock turned on, when I pressed 7 on FC210TP, I saw the following sequence of keycodes on xev.

KP_7 -> NumLock

I didn't check further, but I suspect it was actually "NumLock -> KP_7 -> NumLock".

This is not problematic on linux virtual console, but numlock is sporadically turned off on Xorg when I press number keys fast.

My suspicion is that the following sequence of keycodes turned numlock off sporadically.

NumLock_for_KP7 -> KP_7 -> NumLock_for_KP_8 -> KP_8 -> NumLock_for_KP7 -> NumLock_for_KP8

Thus, since KP_8 is pressed after the second numlock, Up Arrow is pressed instead of KP_8.

Why is it a problem on Xorg while it is not on linux virtual console and windows? Is there a workaround?