| Too many variables. Is the buzzing across all strings or is it just on one string in each position? Has the bass been setup recently? What is the string height and relief?
It could be a matter of setup. Or it could be a matter of of how true the fretboard is. One of the things that is misunderstood about fretwork is that good fretwork starts with a level, true fingerboard. The same is true of a fretless. It is critical that the fingerboard is level.
Sometimes, if there is a very small anomaly in the board the neck can be adjusted so that the hump does not come into play. | 
