If I were to guess, they had engine problems or overhauls done at open sea (and if I'm to be evil and speculate, in international waters where the pesky authorities have no say and can't invoke the extra scrutiny for ships running under convenience flags - Panama is both on the French black list and US target list).
I still doubt they'll make New York on the 13th, though, but a few days extra, we can live with!
I'm saddened that BMW do hire ships that run under convenience flags, though. I'd rather pay a few hundred bucks more. But, anyhow.