If I were a betting man, which in this case I am not, but one with rather a lot of experience of helos and their issues, I would guess, from the results of the accidents, that the March in JB was the result of a mechanical while the fatal was not. There are some fixes to problems which can take many months to develop, and then more months or years to implement; and in the other space some inherent aircraft limitations which mean that whatever you do, that limitation will remain. I have no experience of high speed flight over water at was apparently low level and at night in an MRH-90 but in any helicopter (or fixed wing aircraft for that matter) that is always regarded as a high risk flight regime, particularly if the sea is very calm. But we will have to wait to see what relative weights the AIB assigns to the mechanical and human factors in each case. But the grounding was, at least initially, certainly the only correct approach until at least preliminary assessments were available.