I have this Cort KX5 here, bolt on maple with rosewood neck, tune o
matic type of bridge. Fretbuzz start to occur form fret 7-17 while
neck bow clearance is fine. There appears to be a hump starting from 7
to 17 (neck/fretboard, and thus frets), and it even remains there when
I adjust truss rod until a straight neck. in that case, my stewmac
notched straight edge makes contact from about 2-6, then I get worse
lift off, until it makes contact again around 13 (max of the hump) and
then takes of gain until the end of the fretboard. Releasing truss rod
further does not make the situation better.
I thought I'd fix this kinda "Fender hump" by placing a shim under the
top 2 screws in the neck pocket, but since the hump is already halfway
the neck and not around the bolt-on zone, I guess it is not going to
help a lot. Compensating the hump by filing the frets extra in the
hump zone seems a risky job, and as far as I can see, which 'll make
it a worse job, it should be done while the instrument in stringed up
with neck under tension so I know how much to compensate.
Here a picture of the neck in situation with good relief. You can see
the hump with the naked eye.
This is with the neck straightened. It is +/- straight from 0-12, but
then you have this nick that stays.