I would think several stitches in one place would lock them in without worry, that's basically just a small knot the machine makes, which I know there are some that actually do put a knot in the beginning of a seam.
Maybe take a piece of scrap, sandwich it up and stitch it like you are going to and then test it to see if they are locked. If they are, then you know you can stitch without worry. If they're not, at least you find out now versus finishing your quilt and the stitches come undone in a few weeks or months.