I'm not sure if you've already considered this or not.... but I have an Idead of what might be going on.

The sounds you describe may have an filter or amplitude attack that lasts maybe a second or more. The attack is the time the sound takes to get up to its peak level after the key is pressed.

If you don't hold the key down long enough, the sound won't reach it's peak level. When you hit the notes staccato, there would be no way to hear the peak volume of the sound.

One solution is to decrease the attack time to zero or even to negative values. This should allow you to play those sounds staccato and still hear them.

Hope this helps.... Moon Patroller