I had the same smell one time coming from my offset. I was freaking out trying to figure what it was coming from. My first thought was that something was in my charcoal, I took all of it out spread it on the driveway. Nothing but hot burning coals. Started looking inside cooking chamber and under the piece metal that I have to make a reverse flow there was a melted flashlight. My son at the time 3 yrs old said thanks Daddy for finding my flashlight.
My arsenal, Stumps Clone, Two Modified offsets, open pit with grate and rotisserie,UDS, and a free to me Weber One Touch Silver 18.5" kettle