Once again, referring to Mahon's quote:
In my opinion, neither Captain Collins nor First Officer Cassin nor the Flight Engineers made any error which contributed to the disaster, and were not responsible for its occurrence.
3 Holer says:
That is NOT saying the crew was blameless, that is saying the crew did not make any error which contributed to the disaster!
And 3 Holer also says:
My point is, Mahon never attempted to blame any person(s), throughout the whole inquiry, for this accident.
So if I understand you correctly, your interpretation of Mahon's statement that the "crew made no error" does not mean he's saying they were without blame. However, no party is actually blamed for the accident either.