Thanks for chiming in Macker.
As for the MIDI In Port - Setting that to Off means I can't use any of my MIDI interfaces (MIDI keyboard, faders, etc…) And even when I turn it off, stuck notes still happen. Good to know that could be a thing to check if I run into problems later on though, so thanks.
I'm pretty read up on Logic's manual, and I've been using Logic's multis and aux's for a few years now in tandem with VEP with no issue until now. So I'm gonna go out on a limb here and guess that most of the problems I'm facing right now are on Logic's side of things, and not VSL. So until there are some fixes from either end, I'm unfortunately going to just put VEP on the shelf for now and go with a disabled track template in Logic.
Thanks to everyone who tried helping solve and narrow down these issues with me!
@Macker said:
KeplersConundrum, in your picture of Logic, in the Track Inspector I notice MIDI In Port is set to All (the default setting). Unless you have an exact and specific reason for having that default or any other active setting there, I'd strongly suggest you set MIDI In Port to Off on all tracks. That way you eliminate the possibility of an inadvertent howl-round event loop occurring, however momentary it may be. No guarantees, but at the very least it's good practice in terms of 'realtime-system hygiene'. I've no idea why Apple would choose the most potentially disruptive setting there as default. (It's embarrassing now to think of the many times I fell foul of that problem when I first started working with IAC Busses - or "ports" as they're now called - back in the old days when eMagic's Logic behaved impeccably! Lol.)
Anyway, you've done well to isolate your problem to your usage of Out Port 1. Now you have the option of simply avoiding usage of that Port - unsatisfactory and even annoying though that may be. Otherwise you might get caught up in endless nugatory investigations at home and fruitless dialogue here (likely as not for the benefit of some interlocutor's ego and public image cultivation rather than actual benefit for you.)
Oh, also, in answer to your last question above, the additional mixer tracks that get inserted each time you press the little + button on the 'mother' instrument track strip are in no way interactive with the track's Port setting. This feature - sometimes flakey in recent Logic versions - has to do with separately-numbered audio channels returning from VEP. It could of course become part of a special - 'virtual' - multitimbral setup a user might organise for Logic and VEP; but that setup and usage can be tricky and, as far as I'm aware, is very far from typical usage. Have a read of Logic's Help files on instrument mixer-strip aux tracks, etc.; that should set you on the right path without you having to answer endless questions about what you're doing and how you're going about it.