This makes it sound as though there's a widespread,
inevitable problem with shoe laces --and I've not ever
heard that (and marathon runners don't all wear Velcro
stuff, do they!).
For a surer knot, one can draw down the original bights
onto inserted-within-them 2nd bights which thus act
qua toggles on the originals coming untied. This can
be done in a sort of swallow-tail orientation (i.e., so
both tails run down the shoe towards the toes, not
one so and one going away).