The complaint does not allege that the Logitech wireless controller, the carbon fiber construction, Titan’s innovative porthole, or the use of disparate materials with differing expansion/compression coefficients—four main areas of criticism—were individually responsible for the sub’s implosion. But it does suggest that these systems could have together contributed to a “daisy chain of failures of multiple improperly designed or constructed parts or systems.”
It’s using the fact that it was a wireless controller used over Bluetooth as part of the evidence that they created a bunch of unnecessary points of failure.
It appears they are suing OceanGate, the company that made the submarine. The use of cheap, consumer grade hardware for critical functions (literally controlling the sub) is one of their criticisms.