Korg Legacy M1 in multi mode in Logic?

Multiple outputs are a feature that is not implemented in the M1 Audio Unit plugin - it's Korg's fault, not a problem with Logic.

It is implemented in the VST format plugin as far as I recall. It just isn't implemented in the Audio Unit version, for whatever reason...

Probably the code to route to the extra outputs is still there (hence why the sound drops out), they just didn't do the extra work to define the plugin as multi-output capable - hence it only presents a stereo-output version to it's host...

Anyway, the M1 is quite CPU efficient, so you might as well just use 8 individual instances in performance mode, rather than multi-mode (multi mode was really only a way of getting as much out of limited resources as possible, and was sub-optimal in most instruments due to lack of effects and other things - in these enlightened days, we don't have to deal with the same resource limitations of old like limited polyphony, single effects units, and so on...)