I read the report last night. you can't see all those incidents without it raising concerns!
The report with the tape recording doesn't eliminate the possibility of an abrupt control input, eg. student reacts to a bird, rotors can impact in less than 2 revolutions, instructor is helpless.
The report does still allows for the possibility of a number of different scenarios adding up - a few low RPM stall with reaction times not quite met, a few turbulence or low-G, a few abrupt inputs.
The improved safety awareness by RHC has improved the safety massively which, to me, indicates that some of the incidents must have been due to these causes.
However, a few of the incidents were high time pilots in good conditions. As a low time pilot, it makes sobering reading, and I find it hard to believe that all 31 incidents were down to the pilot's actions (or inactions), but thousands of hours of research by accident have failed to turn up any fundamental problem.
It has to be a possibility that there is a flaw there, but far brighter minds than mine haven't turned it up.
BW