Dragon enjoying ISS stay, despite minor issues - Falcon 9 investigation begins [NASASpaceflight]

The first stage issue related to Engine 1, one of nine Merlin 1Cs, after – it is understood – the fuel dome above the nozzle ruptured. The engine did not explode, but did cause the fairing that protects the engine from aerodynamic loads to rupture and fall away from the vehicle due to the engine pressure release.

It is not clear if any specific details into the root cause of the failure will ever be revealed to the public, due to the proprietary nature of SpaceX’s hardware. However, NASA and SpaceX are currently reviewing the incident via a joint CRS-1 Post-Flight Investigation Board.

"fuel dome"というのは燃焼室の上にある部分のようです。ここが破損してエンジン内の圧力が低下しエンジンカバーが脱落しエンジン停止。