Artist list isn't complete

Hi I've been having this issue for about a month now, where the top artist list skips over many numbers. It varies but here's an example . . . It starts at 1 then then skips 2 and shows me 3, then it skips again to artist 7. So instead of having a list that goes like this: 1,2,3,4,5,etc. It's usually like this: 1,3,6,7,9,11,etc.