I have a Gretsch with an aluminum nut and the strings seem to be getting stuck in the slots as they exit the nut towards the tuners. Tuning up, the string pitch suddenly changes with a “ping”. I’m constantly fighting to get the string to come into tune since it keeps binding up in the nut. I use a lubricant that helps but I was wondering if smoothing the edge of the string slots with a diamond file so there’s not a sharp angle where the strings come through to the tuners would help. Are there any tips, advice or recommendations on what to do to fix this tuning problem? Thanks!