It's a big complex project that legislators decreed should re-use ancient engines and structural components from the shuttle - a project that was the world's first space-faring barrel of pork, infamous for its operating expenditures.

One of the arguments for doing so was that the engines were "proven."

checks news story

Oh hey, it's the engines that are causing these delays.

NASA has been so over-budget on the project, they had to commit accounting fraud to try and cover it up.