[QUOTE=MurphyWasRight;10304564]From the picture it seems improbable that both locking means were missing/misinstalled.
There is a more subtle issue of the effects of the washer (140) either missing or on the wrong side. This would not jump out on a visual inspection like missing locking means would.
I have no experience on this helicopter type (but 43 years on many others).
In most mechanical assembly situations a washer is placed "under" a nut, and looks "correctly assembled" when inspected, but it is the opposite in this case.