Hi, I've got this problem relatively often (maybe a batch out of five?). I don't bake american sugar cookies, but use HoneyCat's shortbread-ish recipe (slightly modified). I've noticed I have it more with rerolls (it's a recipe that doesn't reroll well at all), and more if I refrigerate the cookies uncovered (or let them sit out uncooked on the counter for too long). But I've also had it on first rolls, baked immediately. So I don't have a definitive answer. When I do have the issue, I scrape/microplane the flakes off the cookies and wipe away the crumbs with a large brush. It's a pain, but the cookies always taste as good and are fully useable.