If an overfilled flour bowl causes the flour to back up, this may jam the grinder. There is leftover grain or debris in the grinder.When the mill is running, change to the “coarse” setting and allow the grinder to run without any mill feed.If necessary, open the grinder and remove any leftover flour and/or debris.If the grindstones are heavily laden, clean them with a dry, hard brush.Refer to the Novum Grain Mill HM-NOVU user manual for more information.