Pad selection doesn't work

Hi guys,

got a brand new MPC500. When I select a pad, e.g. in program mode to assign samples, and I press a pad, the display behaves weird: Sometimes it switches to the right pad number, sometimes it shows some other pad number (e.g. I press Pad 1 and it shows pad 12). Any idea what this could be?

Thanks,

yours AmbientHunter