When you do 100 sales in a day its not easy looking through every single box for every single tiny part. Most of the time it's a simple, open the box and makes sure its not broken in terms of glass cracks and that it powers up, that is all.
Ive run a couple businesses and I know how hard it is getting parcels out on time with people breathing down your neck! You take one extra day looking parcels over before shipping and you get yelled at by the customers for not having the parcel out on time!
The RDS stopped working AFTER a time... so they would have checked it to see if it worked, it did, end of story and it was shipped off. That is a manufacturer defect, no fault of the website.
As for the part missing, that is the fault of the manufacturer although MAYBE the website dropped it while testing to make sure it worked.
The only time Id blame the website for the same problems this guy is having is if the website refused to offer a refund.
Im not taking buyairsoft.ca's side in this because of personal issues, I just know how hard it us to run an online store.
I've had problems like this from online stores such as Hanwei (on swords none the less), walmart, the source, and many more.
IT JUST HAPPENS!