Well many restrictors were really poorly engineered when they first came out. The older GAL comes to mind because the first time it has to work, it bends and then causes clutch problems. The MAC operator restrictor was another piece of junk. Most of them did not have an electrical contact to either shut the unit down or at least act as a secondary door open limit. Therefor you either burned up operator belts or would blow fuses in the door operator do to the fact that the doors were trying to open and could not. They were often a headache for most maintenance men. This lead to many jobs having the restrictor removed or made ineffective. Unfortunately ,the real problem is that people try and climb out of elevators that are often 4 or 5 ft above the floor. This has resulted in many deaths since people have slipped under the elevator when trying to jump to the floor. With the advent of newer codes requiring a longer toe guard the problem is helped but the safest place for any passenger is to stay in the elevator until help arrives. The angle system is probably the most foolproof and mechanically sound. The newer car door restrictors being made today are better but they still need to installed and maintained properly.