Sounds as if you are running out of notes because of limited polyphony. The keyboard will only reproduce a certain amount of notes at one time, and you are exceeding the limit when you layer the organ voices and use the styles at the same time.
It is just a limitation of the keyboard, and not exclusive to yours. All of them have limits but generally the newer keyboards have more polyphony. Also, some brands, while stating lower polyphony limits, allocate the useage differently, so the only way to really know is to play them.
DonM