the most experienced R22 instructor in the UK (circa 8000 hrs on type IIRC) was killed in one due to a low G event and a MR strike on the tail - surmised to have been caused by a FW pilot entering auto by dumping the lever and pushing the nose forward!
Are you sure about this? is it on the report?
From my understanding you cannot get into a low g situation (fuselage roll) entering autorotations.