In the ~2 years you've owned that sectional, you've been billed at least 2x for the privilege of purchasing goods from Costco at profitable prices. That privilege comes with a number of perks, including cheap and delicious pizza and hot dogs, an extended warranty on electronics, and a return policy that is, in the words of the membership clerk that sold me mine "limited only by your conscience."
From one Costco member to another, I'd take that thing back. If you still feel like you need to do right by Costco, consider purchasing the replacement sectional/couch from Costco.