If none of the above tips solve the problem - perhaps the design is not good. Embroider it on something very stable, like denim, to see how it behaves. If it looks ok - then
just don't embroider it on the fabric you've selected before. Choose another fabric. Not every fabric type is embroidery friendly.
In case the design doesn't line up even on perfectly stable fabric and you're sure you've hooped and stabilized it well - delete this troublemaker from your collection forever.
This happens rarely, but sometimes it does. Always make sure you buy your designs from reputable digitizing company. Each design must be tested before it's offered for sale. Be careful with this, because lately everyone and their mother is into digitizing, and some sellers don't care to test stitch their creations.