Enough time has passed that the post mortem reports are underway and quotes from engineers are appearing. The Maverick Design Choices That May Have Doomed Titan

Federal investigators say it could take them up to 18 months to determine why Titan imploded, killing its five passengers. But engineers interviewed by The New York Times point out possible weak points in the sub’s design. . . . What follows is a comparison of Titan’s design with a standard vehicle that, in typical fashion, relies on conservative engineering rules that have proven themselves over many decades. Teams of investigators are now examining such differences in trying to understand why Titan imploded during its dive to the Titanic wreckage.

It includes an illustration of what can happen when dissimilar materials are glued together.

There's nothing new here, just confirmation of some of the main theories.