As a lay person (I have a military aviation maintenance background) my reading of the report was that the investigators,, with the benefit of hindsight were unable to come to a definitive conclusion on the correct remedial action for the reported fault.
I also noted that the recommendations had been rejected by the FAA.
There certainly appears to be grounds for duty holders to be held to account for not ensuring their duties were upheld.
I know nothing of the Spanish judicial system; is it independent or political? There were several passages implying certain recovered components were examined in the prescence of the judge, is this level of oversight normal in similar investigations outside Spain? How well were the engineers able to explain their situation?