One consideration I didn't see suggested is to use a stylus to help guide fabric instead of your fingers.
If the result of your problem is a narrow seam allowance, as sometimes happens to me, I simply turn the block over and re-stitch the end where the problem occurred - start where the seam is in the right place and continue to the edge of the fabric. The original, incorrect seamline is then in the seam allowance and never seen in the final project. This doesn't work if only one of the fabrics slides out of position.