Our QC pick around 1/100 from the assemble department, and check the appearance and leak test.
The leak test way is turn the pumps on the bottle with water, then put that in vacuum container under -0.08MPA and keep 3 minutes.
For the short spring case, as i email to Por before, normally it is impossible happened cause all pumps are assembled by machine, and the marching have the self inspection function, if short any parts the pump will be pop-up to a special place. and our QC manager said it is should be one new worker did not know that and put 1-2 pcs of inject pump to finish pumps!