The plastic scraper left in the wing fold is definitely a failure in tool control, and should never happen (although systems do fail all too often).
The shavings in the fuel tanks is a common issue with new aircraft and after fuel tank maintenance. Those little pieces can escape and hide in places where they cannot be found, until the aircraft flies and sloshes the fuel around. There are fuel strainers for the big stuff and fuel filters for the microscopic bits before they get into engine fuel controls and fuel nozzles where they could cause mischief. Not saying they should be there, but it is almost impossible for the tanks to be 100% clean after manufacture. It is likely the Marines will find some more debris even after their tank flush activity.