DH is a plumber and I read your post to him. He said he wasn't surprised as he knew of the warranty and they are known to stand by their products.
My stepmom recently had a problem with a Moen shower faucet. She called in a friend to look at it and he must have tried to fix it with a part from another brand. And had paid for it. When Pete heard of the problem, he said, "What, you paid for a Moen part to repair it?" Then we found out that the part didn't work and it wasn't a Moen part. Eventually the other guy got his act together and went to a regular plumbing supply house and got the right part and everything is fine now.