My point is that the Soviets mastered this design almost 50 years ago, yet BO is having problems doing it just with a different fuel. Nobody's ever mastered full-flow staged combustion (didn't go beyond testing), yet SpaceX appears further along with that than BE-4, in about the same amount of time. My bet is that it's mostly management issues.

Edit: New news: ULA is having problems qualifying one of the engines for flight because it keeps pumping out too much oxygen. You'd think BO would at least have something like this right before they shipped, but apparently the engines had only minimal testing.

I like SpaceX, but I don't want them being the only cheap, reusable medium+ launch service out there. BO needs to get its act together.