Your post has appeared in the wrong sub but the pressure vessel absolutely was jerry-rigged and the viewport wasn't up to the job: A whistleblower raised safety concerns about OceanGate’s submersible in 2018. Then he was fired.

The report detailed “numerous issues that posed serious safety concerns,” according to the filing. These included Lochridge’s worry that “visible flaws” in the carbon fiber supplied to OceanGate raised the risk of small flaws expanding into larger tears during “pressure cycling.” These are the huge pressure changes that the submersible would experience as it made its way and from the deep ocean floor. He noted that a previously tested scale model of the hull had “prevalent flaws.”
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A day after filing his report, Lochridge was summoned to a meeting with Rush and company’s human resources, engineering and operations directors. There, the filing states, he was also informed that the manufacturer of the Titan’s forward viewport would only certify it to a depth of 1,300 meters due to OceanGate’s experimental design. The filing states that OceanGate refused to pay for the manufacturer to build a viewport that would meet the Titan’s intended depth of 4,000 meters. The Titanic lies about 3,800 meters below the surface.