I agree with the others, it was either too much wood or an improper burn.
If you're concerned with your wood put it in a milk crate and let it sit a month or two. If you have an attic, thats a great 'dry' place to put it.
I have a Kettle where the lid has been out of shape since day one, WSM's too. NO Weber is going to be air tight and you wouldn't want them to anyways. It's just the nature of Weber's and it's not really a bad thing, unless you're trying to save charcoal!