There was a post over the weekend from a new owner whose gasket had slid off on one of his first cooks. Unfortunately, I did not see (and post on) the thread until just before it slipped off page 1. Therefore, I thought I would repeat the story here for those who just took shipment of an Egg.
My gasket (both top and bottom) simply slid off on my third or fourth cook even though it had never been above 400. My dealer said that they have had that happen to three customers in the last month (all brand new Eggs) and have never had it happen in their previous nine years of sales. Obviously, BGE had a bad batch of adhesives.
Fortunately, I have a great dealer. They gave me a new gasket with a can of adhesive (in addition to the self-adhesive) and printed instructions. All at no charge even though the gasket is excluded from the warranty. They told me if it didn't hold they would come to my house to apply the next one. Chim-Chimney's in League City, TX is the best!
So, if you have a new Egg and the gasket slides off, don't lose your temper as I did, and don't blame yourself. Talk to your dealer about a replacement (they aren't expensive even if they do charge you) and put another back on. I am not very handy but had little trouble replacing mine which has worked for two cooks nows - knock on wood.