I have tested the buttons with a multimeter and they all successfully connect when held down. The buttons each light up correctly; the unison patches display the unison LED. The arpeggio rate LED responds correctly.
I also checked the ribbon cable going from the arpeggio knob board to the buttons board and each of these wires were connected properly.
Any ideas what to check? I thought about replace the buttons, but since they connect fine it seems like they should work.