Clipping and Full Clip are bugged in the x64 version. They cause the character to keep falling below the map's surface, even after changing the map and even after closing the trainer. The only solution atm is to restart the game.
Flying option causes the character to jump very high, fall, then jump again high, and so on. This effect is only seen by other players, while you still see it flying normally. But, due to the fact that in reality you jump and fall, then jump, then fall, sometimes when you land on a surface very close to your feet, you die instantly. In reality you might be very high in the air, or if you are lucky, closer to the surface and then you don't die, but you lose pretty much health... Best way to test it is in the guild hall. Try to fly high up, then come down near the waypoint and you are instantly dead