sounds like the same problem that happened with my NJ Classic Bich(neckthru, 24 fret
ebony board,
quilted maple top, $350 new from MF). The 14th fret on all the strings would buzz even with the action half an inch off the board or higher. I looked and measured and noticed this fret was oddly lower than the other ones. So I blamed it on the factory, called MF for a replacement, they were all out and couldnt replace it with a diff color, so i got my money, went to GC, and bought an ibanez. If you have any experience with fretting, changing that fret would probably fix the problem. If you let it go chances are good it will eventually become so low that if u fret at the 15th itll sound out like you're fretting at the 16th. You could also file ALL the other frets down but that's a PITA
Edit: LEVELING, that's what it's called. Yea get your frets leveled and if they're all level besides that one change it out I guess, I'm not really experienced with any of this I'm just going off what other forums told me to do with the Rich