... EXCEPT the D string is wildly buzzy and obnoxious. The other 3 are settling down quite nicely... anyone else have this problem with just the D?
Open string, all over the place or only some positions?
Open string only: the upper nut groove may be too wide
Some positions only: maybe some bump(s) on the fingerboard
All positions: probably defective
You can use the supplied tone filter (small piece of tubing) which comes with the D string for a few uses.
To fix the nut groove problem, just slip the tubing up there in the groove.
That piece it usually meant to be put where the string crosses the bridge crown. It filters out some higher harmonics.
Regards,
François