Hi Groctave,
That's indeed a glitch in Logic's environment, thanks for your posting.
As soon as you trigger the same note on the same MIDI Channel on two different ports, they interrupt each other.
Did you try to switch the MIDI Channels for your second instance yet?
E.g.:
MIDI Channel 1: pizz
MIDI Channel 2: stac
MIDI Channel 3: leg
I don't know any other way around this, and we're all really hoping for AUv3 Multiport to be available in the near future.
Best,
Paul
Paul Kopf Product Manager VSL