Firmware v3.40 replaces the DUAL mode with a new DUOphonic mode so you can enjoy those quints and power chords! If you still need the old DUAL mode please consider using QUAD mode instead setting the Strobe Gate option to on.

Also, as a drive by change: the PitchBend CV was replaced with the AfterTouch CV which makes more sense since Midi2CV Mk2 now supports software pitchbend.