Summary: my 6th string is sharp on every fret while in tune open. Bridge all the way back, and I'm not pressing too hard. I'm putting together my first guitar, with a purchased neck. I'm stuck getting the 6th string intonated. The other strings seem okay. I do have one known issue-- I believe the neck angle is a bit too far back. My bridges (individual ones) are all pretty high to clear the bottom of the neck, but every other string is intonating and playing okay (frets out a bit around 15th fret on 1st string, planning on shimming it, but I haven't yet). I want to say I initially had it intonated okay, and played for a while before noticing the issue. I may be fooling myself though. When I checked it later, it was very sharp at the 12th fret. In my mind, that means the distance from the 12th fret to the saddle is too short, relative to the open string. So, I started backing the saddle down, but even all the way back in the bridge, it's still very sharp on all frets. I replaced the 6th string. I examined the old one, and couldn't see anything obviously out of sorts. It's not me pressing down too hard on the frets. I'm intonating by just touching the fret-- I'm aware of how pressing down to hard can pull things sharp, and I'm not doing that when I'm checking the intonation here. Plus, the other 5 strings don't show this behavior. In my mind, it had to be the take off point in the nut. If it was just a bit back in the slot, the string would be too long relative to the frets. Well, I got my Stew Mac nut files out, and filed that slot so far down I'll probably have to replace the nut, and all the frets are *still* sharp. What else should I be checking? Thanks!!