Odd string buzzing

[Mr Woody]

Let me preface this by saying that, though I'm ne lw to bass, I've been playing guitar for 23 years and have a good handle on doing setups, , neck adjustments, intonation, etc.
But, this one has stumped me!
Just put a new set of LaBella low tension flats on my jazz bass, and got everything adjusted when I discovered an usual buzz. The G-string rings out completely clear on every fret with no sign of fret buzz whatsoever.... Until I'm playing on the 7th fret on the low E and the 7th fret on the G simultaneously. At that point, the G-string buzzes really bad! I haven't found it to happen with any other string/fret combination. I'm sure it's some sort of weird frequency / resonance issue, but I've never seen that before. I know I can keep raising the action on the G-string, but it is already pretty high.

Has anyone else experienced this before? Maybe it's just an odd hump in the neck at that location?

 

[Turnaround]

It's called backbuzz and it is the string rattling on the frets between the 6th fret and the nut. Either damp the strings behind the fretted note, add a bit more relief or raise the nut a hair.

 

[ThomasTronics]

That comes from good vibrations.
Turnaround nailed it. I had that when playing any maj 3rd double stop on the D and G string. Had to mute the string or if you played amped up and loud... you don't hear it

 

[Mr Woody]

A

It's called backbuzz and it is the string rattling on the frets between the 6th fret and the nut. Either damp the strings behind the fretted note, add a bit more relief or raise the nut a hair.

Aaaahhhhh, this makes so much sense! Thanks for that. I guess I never had to deal with in on guitar. Is this why so many bass players use the scrunchies on the nut?