Updated: Mar 3, 2020
When you resize a design without digitizing software, it almost always causes some kind of problem. Editing software is for combining and moving but doesn't recalculate stitch density or stitch lengths. It just moves the stitches. Making designs larger can cause gaps because it moves the stitches farther apart to make the design bigger. This can also violate maximum stitch rules which will cause your machine to skip those stitches. Making designs smaller can violate minimum stitch rules which will cause your machine to skip those stitches too.
A good rule of thumb is if you need to resize a design, make your change less than 15-20%. After you resize, always stitch the new size out on a scrap to make sure it works.