Traktor Keyboard Mapping problems

I'm having a hard time understanding this one. I'm helping my friend map out his internal QWERTY keyboard to some Traktor effects, and all we have so far is G, H, and J are mapped to beatmasher; 50%, 75%, and 90% respectively. The problems comes in when we actually play it. Say we try and do a combo of the buttons, we press and hold G; works fine, then press and hold H; fine as well, then when we press and hold J it doesn't do anything to the beatmasher. We tried all the combinations and came out with the solution that we can only do a combo of 2 buttons on the same effect. Why is that, its very frustrating. And tbh, I didn't do a Google search because I don't even know what to Google. Is it a keyboard problem, software problem, or just an unfortunate coincidence that you cant have more than 2 keys held down at the same time influencing and effect?