Odd Vibration.

[madmatt]

Well my P-bass is acting up. It has actually been somewhat of a problem for awhile but I just now figured it must be something a little more serious.
When I fret my E string at the 12th fret or greater the bass vibrates, it sounds like it is the string, but it is more like the bass. I have changed strings numerous times over the last year and it seems to alleviate the problem for a short while, but it always comes back. I just changed strings twice in the last week and it is much more permanent now. I have strung thru body and thru bridge, flats and rounds, high action low action...
I think it may be the Truss Rod, but when I tap or rap on the neck I do not hear it rattling inside. I just tightened it up and it is definitely tight. Neck relief is right where I like it and the Truss is working (creating, eliminating relief).
So, I dunno, kinda gettin' on my nerves. Especially now that it has become more prominent.

[SurferJoe46]

I have heard of the butterfly-shaped cutouts of the tuning machines setting up a harmonic that can drive one nuts trying to find it.

A drop of CA at the junction of the two metal parts can sometimes resolve this issue.

It may just be a particular frequency that the string produces at that point that sets the vibration going.

[madmatt]

Well I reset my Truss a little (made more relief) and set my string height again.
No more problems.
Not quite sure why the bass started doing this, but now my setup is:
Fender American DLX, GHS Prescision Flats - .045 gauge.
Sidenote: I really like these GHS strings, they are pretty thumpy.