I recall a New Zealand Air Force door coming off in flight. I am assuming that they are built the same as, or similar to a 212. Although pinned back open, the sliders can wear or the airframe slot that the sliders ride in can wear. Either way the gap widens and off it comes. Usually down due weight and rotorwash. Have not heard of one hitting main or tail rotors.
Sorry, forgot to point out NZ Air Force operate UH1's (H model)