Buzz on my acoustic

Hey

I've been getting a bit of work carried out on my Martin acoustic. It started with an annoying buzz when playing the low G note on the E string. I put it into shop to get fixed, and after some work the problem seemed to have disappeared...

but a new one has arrived!

Now i get a buzz that's really weird. When I pluck the D string in an open sounding It sounds fine..... but if I pluck the D string with my finger on the 7th fret of the low E string a bad buzz appears. Weird I thought.

After some investigation today the buzz appears to be fret buzz due to a sympathetic harmonic stimulation of the E string... between the 7th fret and the nut!

So I'm thinking either dampning or raise the nut a smidge. I'm reluctant to raise the nut as I really like the string height where it is.

I will probably put it back into the shop, but does anyone hane any ideas?

Cheers

John