[u]Example:[/u] You map "Keypad 1" with "Reload" and "End" with "Melee".
If you press "End": You will do only your melee attack. Works as intended.
If you press "Keypad 1": You will first melee attack and then you will reload, if you hit the button again between the melee animation.
[u]Conclusion:[/u] The game does not recognize the Keypad as complete seperate Keys, but will always use its "base function" of the respective key first before it uses the numbers, which technically disables the whole Keypad, if you have another action mapped on the same base key.
The only workaround for me so far is to use Autohotkey. My Script looks like this:
[spoiler]Numpad1::5 ; Grenade
Numpad4::4 ; Class Ability
Numpad7::7 ; Air Move
Numpad8::8 ; Interact
Numpad9::9 ; Crouch
Numpad0::0 ; Super[/spoiler]
Hope i dont get a ban for using AHK <_<