From Cracked :
The whole production was a disaster from start to finish. The director, Herbert Selpin, was imprisoned and killed for not being nearly Nazi enough and saying mean things about the German Navy. And only once the most expensive German film up to that point was finally finished did everyone realize that the general public wouldn't really care for a disaster film when Germany itself was being bombed to hell.
The film was pulled from cinemas after its debut and only shown in Paris, before being banned altogether. And then in 1945 the ship the movie was filmed on was sunk, killing way more people than the actual Titanic disaster.
The whole project came to symbolize the complete and utter failure of the Third Reich, which isn't bad for a film where the complete opposite was meant to happen. And to add insult to injury, Germany's enemies the Soviets loved the film for its anti-capitalism message, the Brits stole some of the scenes for their own superior version a decade later, and James Cameron would eventually rip off some of the plot in his own sappy Hollywoodized version.