They tend to have tolerance stacking issues where the excess tolerance in several different parts compounds to create a situation where the hand is trying to turn the cylinder while the cylinder lock is still engaged. When this happens, it brings the whole system to a screeching halt. If you bought it new, send it back to Heritage for repairs.
FWIW, they aren't built for longevity, but they are ok for occasional use.
You don't get to be old by being stupid, but I made it to middle age!