are you absolutely sure you’ve linked part 2 to pattern 4 correctly ? did you press ENTER to confirm the link ?
PART QUICK SELECT To link a part to the active pattern, press [FUNCTION] + [MIDI]. The PART QUICK SELECT menu will appear.
The part currently linked to the pattern is shown with inverted graphics. If a part has been altered but not saved it will be marked with an asterisk. Select the part that should be linked to the active pattern by pressing the appropriate [ARROW] keys. Press [ENTER/YES] to link it. It is possible to quick-link a part by keeping [FUNCTION] pressed when selecting the part.