Erratic timing during vacuum advance

Just remembered an engine I worked on several yrs ago that had a very similar problem. The problem was in the distributor. When the vac advance pulled in the reluctor gap closed up to the point of touching on a couple points (reluctor points aren't always the same height even though they should be) so it'd run real rough. I filed down the 2 high points it had so all points were within .001-.002" of each other and reset the reluctor gap for a happy medium with the vac advance engaged and disengaged and all was good.