Problems with control

Hi, I am working on making a simple game in the blender game engine and I found a glitch in the controls.

The main idea for this game is that it is a two player game, in which each player controls a separate character (one with wasd and the other with the arrow keys). I found that if both W and D keys are pressed at the same time (too move the first character forward and to the right), then the other character will not move forward and to the left at the same time.

If anyone thinks they know why this is happening or how to fix it, it would be a big help if you replied to me.
Thank you,

There is a limit to three simultaneous keypresses in most Keybaords.

Some combinations of up to 5 keys might work, but guarantied are only three (beside shift and ctrl).

I just want to mention my keyboard doesn’t have that same problem, I have just tested that same idea of two players in blender.