It is also possible you just have a bad jelly roll! I once bought two small jelly rolls my daughter fell in love with. They were not from a major manufacturer, and they were dreadful! They were very unevenly cut with a total variation of width of probably 1/4". They also had a bit of a bend in the middle from poor cutting. I ended up finally finishing the jelly roll race quilt she wanted me to make, but it took a lot of fudging to even make that forgiving quilt. Anything that needed accurate piecing would have been impossible. Since then I stick with Moda precuts.