I have to say that I've participated in many COOPS and to this day I don't think I've ever had anything missing ... I'm so impressed with all of them. I've ordered parts myself but found the organization added by COOP managers to make the kits far easier. I've opened up bags (and after doing a few of these kits) ... and finally understand the genius behind why they bagged them a certain why. But bottom line, good post, but the big picture is that these coops are amazing and we can never thank those who run them enough!!
I've also been in many coops. Most have the exact number of parts listed in the BOM.
Sometimes I even get a few extra parts... usually resistors. Usually makes me have to go back and recheck to make sure I installed the correct number of them. If it is a more expensive or unusual part, I'll contact the coop manager to let them know and see if they need that sent back to them because someone else is missing it.
Other times I have been missing a few parts. The coop managers have always been able to get that to me right away once I let them know it is missing. Most of the time, it's the "I had one extra, and didn't know where it belonged, and guess you were the unlucky one" senario.
Have to say the service in the coops are as good as I would get from any store, buying something prepacakged. Sometimes you have a few too many screws, sometimes not enough, and sometimes you just have a screw loose.
Thanks to all the coop managers for all they do!