Im currently in the middle of my first high heat brisket. At first all went well, starting with minon method and got temp up to 350ish. Temp stayed constant until probe temp read 160 which was 2 hours into the cook. I then took the brisket off to put into aluminum pan covered with foil. I put pan back on smoker only to find pan was too big. (rookie mistake). I then cut pan small enough to fit. I put lid back on, but temp at dropped to 225. I expected a quick rise back to temp, but temp began falling with all vents open. When temp dropped to 200, I checked charcoal and saw I still had at least half a ring left. I added about a half of chimney of charcoal and stirred the coals. I cannot get temp back over 225 whats going on?? I started the oven to finish the cook indoors.