There was a similar thread in this forum a while ago. I cannot remember the topic and what the solution was. Hope, you can find it via the search function.

Maybe your keyboard sends some unusal MIDI signals when you hit a key. For example, it sends some controller values instead of only sending the note-on signal. You could try to have a look at the raw input with a tool like MIDI-OX (freeware). If you press a key, there just only appear note-on and note-off signals.