I may have a solution for you. I had this same problem with mine. I figured out you can only go up to a .046 gage string on the low E. Anthing larger than that & you have to adjust the set screw in so far to get it to E from D. As the string gets bigger it takes more tension to tune it up to a given pitch. I went to a .046 gage string on my guitar & it totally fixed the problem. I use Ernie ball heavy bottoms. The E A & D strings are from a set of 10's & the G B & E strings are from a set of 9's. Give it a try. Worked for me!