Thanks for the depth of detail in your response.  All of that comes in handy with drilling down into the deeper aspects.  I tend to push my gear to the limits to squeeze out unusual but useful techniques.

Appreciated; that works well.  Double-click Record in H9 Control; triple-tap LFSW on the pedal … No doubt this will become more easily accessible & intuitive as I put the finishing touches my MIDI pedal Looper template.  You guys did a great job with this algorithm.  The amount of effort put into it shows (special thanks for the rock-solid sync).

Well, if no one else is reporting this behavior, it could very well be system-specific (admittedly, a complex routing here).  I first noticed it with the continuous audio seamless looping.  It's harder to determine when Loop Start begins with a guitar note's typical envelope (pick attack).  I'll experiment some more with keyboard sources, different loop types, and repeated Play retriggers to see if there's a real recipe.