Walk Behind Lawn Mowers

I purchased the HU725AWD walk behind mower from Lowe's recently. When I finally went to use it and looking the mower over to see why the rear door wouldn't seal, I noticed there is a crack in the door along by the spring. Lowe's wants $40 to order this rear door assembly. They mentioned the part maybe covered under warranty and I should check that first. Is this part of a warranty? The mower ia new and never been used? If this part os not covered I will return the mower and find something else. I just paid for this mower and I don't think I should have to pay for a part too. Especially, when it's new. Thanks for any help!