Reply to "Sugar Cookie Dough Consistency with Reduced Sugar and Reduced Butter/ Reduced shortening"

By removing so much fat, you also removed a lot of the moisture content from the recipe, so it's no surprise the dough fell apart. Also, in the process of decreasing the fat and sugar content (both of which have a tenderizing effect on dough), you likely made the dough more susceptible to overworking the gluten in it (higher flour content = relatively higher gluten content). Thus, if you over-rolled or overworked the dough, you could build up gluten more easily, which can lead to a more elastic dough that rises and spreads less evenly (is prone to more bubbling or shrinking).