My old shop, where I worked, we always cracked open any box of paint that a customer bought. If we found any obviously broken paintballs, we swapped out the bag with another one. If it was too oily, same thing. At that time, not sure if it is the same now, we were able to send back broken bags of paint for a credit. Some bags were sealed with simple twist tie, so customers could easily open up the bag and see if there was anything wrong with the paint, feel the shell, whatever. We never minded at all. Although I don't think that I have seen anyone cut open a paintball at my old shop, but it could have happened.