According to the Wall Street Journal, the US GAO (Government Accounting Office) has disclosed that SpaceX Falcon 9 rockets are suffering from a serious cracking issue to its LOx (liquid oxygen)/Kerosene burning Merlin engine turbopump turbine blades, which has raised concerns about their safe use for launching astronaut flights under a commercial arrangement for NASA.
According to Reuters, SpaceX has countered by saying that the engines are “robust to turbine wheel cracks”. Nevertheless, SpaceX also admits that it is redesigning the parts to avoid such cracking in the future. No timeline has been set on this redesign and it is assumed that unmanned launches carrying the “faulty” blades will carry on as normal.

All nine Merlin first stage engines lifts the Falcon 9 off the launch pad with the landing legs seen flush against the stage. Courtesy: SpaceX