Look the user's description and video.

Open the "Main Scene", you should see an instantiated "Door", and hit play! Walk to the door, click on the door handle! You should now see, that the door does not open smooth but instead ugly wobble and shake at the beginning.

Now stop playing, then instatiate the "Door"-Prefab by draging it from the Project-folder and dropping it next to the existing door! Hit play again and try both doors again! The old one should still wobble, while the new door should open smooth (this is the intended behaviour).

Now exit playmode again, save the scene, close the editor and open the project again. Hit play and now BOTH doors wobble. Reverting them to prefab doesn't fix the problem.

If somehow on your machine everything looks great and the same, I made a
video of the same webplayer to proof that on my machine (in the editor
as in the webplayer) the hinge's behaviours are different. You find it here:
http://www.bhone.de/hs3d/LooksLikeThis.mp4
The framerate is low because of the capturing, but the behaviour is the
same with 50 fps.