This fella reckons the design is the problem.
BTW was this recent Fury Mike's red one ?
This seems to describe the problem pretty well. And yes it's Mike's old one. It's a lovely bass that I'd really like to get going.
Should you level? At this point, no.
A general rule is that buzzing above the 12th fret is due to bridge saddles being too low. Buzz lower down on the neck... you can assume is relief related. There are other factors, but I’d need the neck in hand. If the action is too high once you’ve gotten the relief where it should be, the neck tilt is correct, and saddle height raised to where the buzz goes away... then you should could consider fret leveling.
I set the relief to 15 thousandth of an inch at the 7th fret with the string capod at the first fret and near the body. Then I've got a lot of travel with the saddles but can't lower them really at all without the buzzing and choking out starting at about the 14th fret. To violently change from imperial to metric, I can't get the action any lower than about 2.75mm at the 12th fret.

WANT!