We are getting back to the story that somehow this aircraft had a will of it's own, and there is no evidence for that scenario.
Well, no, because there was not enough left to discover conclusive evidence, (although some possible indications) and no flight recorder/cvr.
But there is sufficient evidence of other Chinooks having a 'mind of their own', both flight controls and FADEC, to include it as a possibility.
There is no direct evidence available of a deliberate cover up either, but there is enough circumstantial evidence from the behaviour of some of those close to MOD at the time to make one wonder.