If your customer finds a flaw in a frame you built, would you want the customer to bring it back and give you the opportunity to make it right, or would you prefer to have the customer only complain to friends, your other potential customers? Or, if your customer's neighbor calls you to say she heard your framing was defective, but your customer never mentions it, what good would it do?
...I have sent back glass to LJ even after it's been cut. They took it back, no problem and gave a credit for the bad glass. It doesn't matter much if it's been cut or not...
Kudos to you. Yes, it doesn't matter whether or not the glass has been cut, and that's the way the warranty works. Neither the distibutor nor the maker expects any framer to use a defective product.
Remaining silent about a defect cuts directly into your net profit. You buy it, you handle it and you scrap it with zero return? You might as well feed those dollars into the shredder. Asking for replacement is an inconvenience with a cost, but a minor one, compared to throwing the money away.
Aside from the total loss of your money, letting the manufacturer off the hook only perpetuates the problem. Complaints without the exchange of product are worthless, because they typically do not go up the supply chain. But if they did, it would be a marketing problem, not a quality problem.
Insulating your distributor from having to deal with a defective product would be counterproductive. Distributors would rather have an opportunity to keep your business by replacing the defective product, which provides an audit trail of defects/replacements for them and for the manufacturer. Prove to them that the problem exists, and make them pay the price for it.
Of course, a framer could simply refuse to sell the glass. But that would only deprive customers of the premium product's benefits, as well as reduce the framer's revenue and profit. For most of us, that would not be a winning strategy.
It doesn't matter whether we're talking about glass, matboards, moulding, or any other product we buy. Instead of insulating from loss those reponsible for the defective product, taking the whole loss yourself, and complaining, send it back for replacement.