Top flue cover plate of stove bent

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I bought a Stanford 80 Nestor Martin multi-fuel stove in 2009. This month I've noticed that that top flue cover plate has become bent (and almost split in two). I'm not able to remove the screws that are holding it in place because they've almost disintegrated and I can't open them with a screwdriver. I intend to ask the retailer about the problem but has anyone else had an issue? BTW I'm attempting to attach a photo of the problem but I'm not sure if it will work. Thanks
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