i have also been having a little problem with the action of one of my guitars.
its a set in prs style guitar

my problem is the action of my guitar can't get lower than .6 centimeter and my personal prefference is action lower than that. if it goes any lower it starts to buzz on the higher frets.

i took it to the guitar shop because i thought it was the neck causing this problem but they said the neck's perfectly straight, and the neck is connected to the guitar at an angle. the neck is raised a little bit. and still that didn't make any sense that i can't have the action any lower because if the neck is straight, the strings would be parallel to the fretboard when i lower the action.

example 1 is how it is now (the neck's angle is exaggerated)
example 2 is what it should look like when i lower the action



but when i lower the action, there's buzzing on the higher frets and it doesn't make sense.

is it cause my frets aren't even?
is it cause my nut's too low?
it can't be the nut cause the nut wouldn't effect the upper fret buzzing
and i don't see why the neck angle would be bothering this cause i could lower the bridge so the strings are level and parallel to the fretboard.