Sub 37 SEQ Mod only

[Lymtronics]

I'm trying to use the sequencer as a modulation only sequencer with free use of the keyboard in duo mode. I can set the modulations up so I can play notes normally on the keyboard while the sequencer steps through the values I've set with the mod wheel in step edit mode, but duophonic play on the keyboard does not work consistently. At least half of the time just a single note plays with both oscillators. Any advice, or is this maybe a feature that needs to be ironed out?