I believe I have figured out why Vienna Multi port mode will not function correctly with Logic Pro. There is a bug in the environment layer of LPX. Specfically, the transformer object will not insert CC99 with the fixed value for the port number. It does for NoteOn's and other event types, but for NoteOff, it always inserts zero for the second byte even when VSL have provided an environment layer that is supposed to be setting that byte to the port#. This is clearly a bug in the transformer object of Logic Pro. its also creating duplicate NoteOff's, all of which is confusing the VEP plugin.
Good luck getting Apple to address that bug, as its in very old code from the old Logic days...but anyway, that is the problem.
SOLVED: I have come up with a work around, See this link for explanation and free downloads:
https://www.logicprohelp.com/forum/viewtopic.php?f=9&t=137085