I own a 07' Cedar Creek(Forest River)Daydreamer and I can't say enough about CC's after-the-sale customer service, any time I have needed them they were there in spades! Last summer I noticed the clear-coat on our full body paint was flaking off and after short call and a few photos Cedar Creek arranged to have the whole fiver re-clear coated at no expense to us and keep in mind this is an 07' fiver well past any warranty, they said they couldn't have one of their products looking like that!
Not knowing all the details pertaining to your situation I do find it hard to believe they won't cover the glass door and I wonder if perhaps you tried another customer service agent they might do better by you and send them a link to this post reminding them of their "Creekers" who are supporting them and are expecting them to not make liars out of us!
GOOD LUCK!