Maybe sometimes you are getting forward ribs, and sometimes getting rib too close to the tail end?
I can't recall getting any bad meat from Costco here. But I get most of mine from Sam's Club, and been really happy there.
Now, the Son and Daughter-In-Law are fairly strict Wall-martins, and they get bad meat a lot. I've looked at Walmart, but their meat is all painted. I bought a bag of frozen Salmon there once. It was little scraps with the skin on.
So I use Walmart for hard goods and canned goods, when I need less than a gallon of something. LOL!