If you try this: select patch F1 P1 LosVangelis2041, then press the Split A/B button, then press it again and hold it whilst playing a key on the keyboard and release the Split button. You should end up with a simili-string patch on the left part of the keyboard, and the same sound but with an added arpeggiator on the right side when hold notes.
If that doesn't happen, then there's something wrong. BTW, do you have the keyboard version or the new desktop ?