Self-ratcheting / auto-ratcheting is a fast but dangerous and foolish way to lower loads.
Under certain load conditions with the hoist in the lower mode, a flip of the handle can result in a rapid back-and-forth motion.
This is a result of a match between the load mass and the natural oscillation frequency of the handle.
It results in a repetitive and rapid-fire impacting of the hoist, and other rigging as well, that a hoist is not designed to withstand.
Lowering of the load should always be accomplished through manual jacking of the hoist handle.
Safety Inspection Tips, Maintenance and Use of Strap Hoists information available here:
Hoist Safety, Tips of the Trade
Hoist Safety, how to inspect, test and maintain..