Hey , i'm in need of some help / advice. I have a Les Paul style guitar that is giving me intonation problems. First I should say I adjusted the truss rod to where it's supposed to be, adjusted the height at the bridge , set the intonation, and chords still sound off. I'm using a very good tuner. at first I intonated each string at the 12th fret, but it still sounded off, then I read it's more accurate to intonate at the 24th fret, so I tried that. and to my surprise it actually sounded more in tune. but still with the same problems as before. I noticed that some lower frets sound sharp , like especially on the 3rd fret on the A, but higher frets are actually in tune. Is it the nut? It seems somewhat high. How can I fix this? Is it hard? Can I just sand some of it down?