I really just didn't like the feel of how it played. It also sounded very tinny...
What do you think it was in terms of the playability that was different about that one? Was it setup ok? Problems with string tension? I'm just curious. With CNC machine-made instruments there should be very little structural differences from guitar to guitar. Makes me think it was either a fluke (warped neck?) or some human error in set up. Either way it's weird that six basses were fantastic and one wasn't.
FWIW I like the Millenniums so much in terms of playability I would likely pick even a badly set-up one over a well set-up but unbalanced tree limb that some people play.

, Hipshot open gear Ultralight tuners (instead of Hipshot Gotoh style tuners)
and a standard Hipshot Bass Xtender on the four-string models.
Otherwise they are the same.