The backwards compatibility is not as it should be: https://www.gearslutz.com/board/electronic-music-instruments-and-electronic-music-production/1258509-kurzweil-pc4-73.html
And other PC4 users here, can you check and verify this very issue please?
See: https://www.gearslutz.com/board/electronic-music-instruments-and-electronic-music-production/1258509-kurzweil-pc4-74.html
Quoted: "Can someone check: start an empty patch with a blank keymap. Editing the keymap on a given key. Start from sample 3300 onwards which is Applause. From there on every next sample is wrong or not sounding at all..."