What is often unrecognized is that launches put their vehicles and payloads through severe vibration and high g-forces that can easily damage spacecraft. A propellant line fitting seems to have weakened or failed.
And THAT, buoys and gulls, is why we do Vibration Testing and Acoustic Testing, at the component, subsystem, and system levels.
And that costs ...
Cut corners on testing, maybe get a "sub-optimal" result.
I don't know that they cut corners. I do know that cutting corners has led to failures in the past.