Biggest mistake of Indonesian investigators was to let Boeing & NTSB fella get their hands on the acft parts and FDR/CVR...some " magic " happened!
Sadly because of the state of corruption and disorganisation in Indonesia, local investigators were treated like buffoons. So to get some credibility, they naively handed over a lot of things that could have exonerated the skipper to "people" who worked " magic " over the evidence.
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No "magic" was worked on the evidence. I was there when it was recovered and physically watched as each flight control component was examined by investigators from all countries taking part. Both the DFDR and CVR were escorted by international teams to the NTSB for analysis.
No magic could have exonerated the skipper. He did it all by himself.