Whose side are you on, Welsh Wingman? He who sits on the fence as regards Erebus eventually ends up with a wooden post up their arse.
Mahon's report was garbage and it contributed very little to aviation safety. His finding that the crew were blameless was demonstrably wrong (and it appears that you would agree).
The so-called "alteration" of the CVR transcript had nothing to do with anything, despite the attention given to the subject by Mahon.
As to the alteration of the waypoint, Chippendale's finding appears to be very strange but it's explainable if you go into the background and into the initial statements made to him by other pilots. That said, it's obvious, in the absence of evidence of a murder/suicide, that the crew thought that Erebus was out to their left, not dead ahead. Was that assumption justified? Definitely not. Where was the waypoint, in fact? McMurdo Station. Where were they told, at the briefing, where the waypoint was? McMurdo Station. Where does a track from Cape Hallett to McMurdo Station go? Over the summit of Erebus.
Anyone who thinks that some old flight plan that might have been floating around at the briefing exonerates the crew is living in cloud cuckoo land.