S76 was destroyed by this practice a few years back
We had a pretty noticable accident a few years back of an S76 being completely destroyed (Villahermosa, Mexico) as the pilot left the acft and it rolled over by itself, I don't know how exaclty, maybe Nick knows a little more about this incident.
I myself have to do this very often, for various reasons, to take a leak, up or download pax, get my camera, etc. etc.
On I DO friction the thing tightly, I used to take the HYD out, but have stopped doing this recently due to possible motoring, and always at idle, never at 100% NR.