The hook coming loose sounds a strange problem.
Mine (Mountain Trails??? I can't remember) are strongly elasticated around the lower edge and are pulled down tightly over the boot by the straps under the instep. They are designed so that when they're zipped up the circumference around the lower edge limits the amount they pull down, and this keeps them tight on the boot. So in my case the hook has to be pulled hard to fit it over the second row of laces from the toe (but I've not experienced the hook wearing the laces).
So what can be wrong with the OP's gaiters? He says he's worn ones for about twenty years and he's tried about ten different adjustments, so presumably he knows what he's doing. All I can think is the circumference around the lower edge of the gaiter's he bought is too large for them to be tighly sitting on the boots, or the strap under the instep doesn't hold them down tight enough. Perhaps they are a really poor design, with the hook placed too far forward.
What make and model are they mate?