I worked three decades in aerospace and you would think this would be simple to follow procedures. I can attest that it is anything but. Especially with vac fill procedures. We had one piece of space hardware that we made a rotation fixture to reorientate the hardware as we did the oil filling after pulling a hard vacuum. Was amazing to watch the air bubbles appear after working them through the maze of plumbing.But how the heck do they mess up this step at the factory?!.
edit: many mistakes are made from rushing the procedure. takes time.