i often get that they just do old problems over and over again. And i've realize that students don't ever get training in how to study for mass. So when i probe them, i find that the structural stuff is not at all coming through to them. I have created assignments, or i give them a bunch of problems that are very similar. That really helps them get to the structure. It's not instantly, because this needs practice, but at least it starts them sinking in that direction.