I'm confused. If the knife you got is not worth them checking for the problem, then how is it worth the effort/expense to return/exchange it? If you are simply looking for a function check that would take all of what? a minute? The shipping was paid by someone, and I bet they sell most of those bargain bin blowouts to guys who will throw them in the tackle box, or grandmas as gifts for the grandsons who "like knives" If there is any chance that you would care about it, then A)Let them know you care, or B)eat the cost of the knife and forget about it. I feel like I'm missing something here, including how this thread got so blown out.
I would agree that asking for a them to give a sebenza level QC job to a 20$ knife is a bit over the top, but I don't see anyone suggest that. Generally the advice is to ask for them to check what's important. Part of the Forum is finding out what aspects of knives are just not worth worrying about because that "flaw" is inherent in the design, and you decide to live with it, or walk away.
People complain about QC in $300 dollar knives because at some point you expect that they have that part worked out, unless the raw weight of the materials is $290 and the maker could only invest 0.75 into actually manufacturing.