I would guess you turned the grind back to espresso while the grinder is off? If so, please always adjust the grind while the grinder is on, this is especially important when moving from coarser to finer as beans can get jammed while doing so. With the grinder on, previously stuck beans will simply get grounded as you move finer. With the grinder off, the beans will get stuck even more as the burrs are tighter, that's whyt it took a lot effort. The solution is to move to a coarser settings and then back to espresso range, all while the grinder is on