J.M. Also not knowing how old the unit is, Some have a plastic nut on the bottom of the unit. This either will loosen or tighten tension on the "clutch" spring. If this has this type of adjustment, it appears to me the clutch spring needs to be tightened. You might remove the cover and also check the clutch out. On the older models I believe this is about the only safety feature there is. Don't get it so tight that it will not reverse upon hitting an object.