The hull of the Titan vessel "showed signs of cyclic fatigue," according to a January 2020interviewwith OceanGate CEO Stockton Rush, who is aboard the missing vessel. Rush told Geekwire that due to that stress, the hull rating was downgraded to a depth of 3,000 meters, 800 meters short of the Titanic's depth.
https://www.nbcnews.com/news/world/live-blog/titanic-missing-submersible-live-updates-rcna90103
