Hi Greg,
pre-roll has been off, and toggling it doesn't have any impact.
I did some further "tests" with a 2-bar 4/4-loop with my kick audio event on a dedicated track as the reference using the following VM setup

- Cubase 10 Pro_VM setup.png (477.66 KiB) Viewed 9402 times
Scenario 1: the Cubase loop region spans exactly the 2-bar audio event/sample.
Scenario 2: the Cubase loop region covers 3 bars with an "empty" bar ahead of the 2-bar audio event/sample.
In both cases I always see a delayed VM-Kick audio output. Interestingly the offset varies slightly with every round (just hitting "1" to restart the loop at the left locator). From the guts, roughly every 10th attempt both kick tracks are "almost" in sync.
This is starting to become a real issue for me. I hope you can analyze and fix this issue soon. If you need further support, I'll gladly help wherever I can.
Cheers,
LiteOn