When the cradle is cranked down too far it can cause slack which allows the cable to spool out and get caught between the chain and sprocket. The next time it is cranked up it kinks the cable and either stretches or snaps the chain. If your chain is slipping or if this has happened in the past and you will need to replace the chain. The cable should also be checked to make sure it is not damaged.

Another possibility is the winch is over weighted or the sprockets have become worn.