Based on what I saw in my trainer, here is why I think that Jetblack made a fatal design flaw on the Victory:
Ideal Design: This is how the screw that connects the flywheel to the belt drive along with the washer should look like: A well-fitting washer (blue) where the inner diameter fits the flywheel screw (grey) and the outer diameter fits into the inner belt drive (black).
This would make sure that the axis of the flywheel is always well-aligned with the axis of the belt drive, reducing the likelihood of the flywheel being off-balance and minimizing vibrations.
Actual Design: But this is what they actually did instead: The washer (blue) neither matches the flywheel screw (grey), nor does it match the belt drive (black). As a result that causes the risk that the axis of the flywheel might end up being more or less aligned with the axis of the belt drive. Similarly the axis of the spacer might not align either, but is less critical due to the small mass.
(Dimensions are obviously not to scale and overstated to explain the issue.)
It effectively becomes pure luck how much your flywheel is off-balance and how much vibrations you end up having or if you feel that vibration or not.
To prevent this the factory would need to find a way to align the axis of the flywheel to the axis of the belt drive and tighten the screw while that alignment doesn’t change. Call it individual calibration per trainer.
In my case based on the “dancing pattern” of both the inner screw and the washer, I can tell that they are both off center with regards to the belt drive. Therefore there is definitely no “calibration” that happened on my device. And as a result I get vibrations, that vary based on rpm. 
Your device will most likely look different and therefore cause you more or less vibration. Or the vibration is below what is noticeable.
Of course it’s possible that the actual design called for a better fitting washer and the factory installed something else. While that’s then not a design flaw, it doesn’t make the result any better.