My go-to guitar. It had fret buzz on two strings (?A and D) up around 10-12th frets. It was otherwise very nicely set-up and stable.
I took it to Danny Shoemaker at Straight Frets. He put it on his bench and we looked at it together for 10 or 15 minutes. He thought the neck had either twisted or swollen a little unevenly over time (I can't remember his exact theory). Long story short: I decided to just get it PLEK'd, and left it with him to PLEK and put on a new nut (the machine can also cut the nut with perfect precision as it levels the frets).
Before I left it with him, he let me look at the machine and showed me how it works. Once you lock a guitar in place, the machine will measure out everything very precisely and print out an incredibly detailed before-and-after schematic of how "off" the frets are, how much metal is going to be shaved to get to the ideal configuration... like down to the tiniest amount of metal along every single fret. Then you can pull the guitar down and tweak the truss rod (and maybe also tweak the bridge). Then lock it back into the machine and let it measure everything again. I think the idea is to get it set up by hand as perfectly as possible so as to shave off the least amount of metal.
I picked it up a week or so later, and he confessed that his theory for why I had a little buzz in one spot wasn't exactly correct. It made me respect him more that he would readily say that.
I've got to say, if it was world's best luthier vs a really good luthier and a PLEK... I'd take the PLEK all day long. They're incredible machines.
Y'all have seen it more than once on this thread... it's a 91 Custom Shop. It looks a little red in this photo... it's actually orange. It also got relic'ed the old fashioned way - by playing the shit out of it for 30 years.