The bottom line is that I didn't pay careful enough attention to my ET-733. I set the alarm, but I must have accidentally turned it off. All went well for the first 2 hours or so. I put it on the smoke at about 9:15pm planning for it to smoke overnight. I laid a snake weave and set the Weber OTG up right for smoking. Got the fire up to temp before I put the brisket on. IT was behaving and chamber temp was OK. I went to bed about midnight knowing with a certainty that my Maverick would let me know if any temps got out of line. Apparently the chamber temp went way too high. I got up about 3:00am and took a peek at the Maverick. It was not good. I took the top off the Weber and saw that the coals had almost burned completely up. They should only have been about half burned after 6 hours. The brisket looked like a lump of coal.
I brought it in and wrapped it in foil and an old beach blanket, then went back to bed. When I checked it about 8:30 I knew I would only be able to save a small part of it and then only if I chopped it slathered it in sauce before eating it in sandwiches. It's almost good and mostly edible.
Oh well! Another lesson learned the old-fashioned way!