Dr_KY
Quintessential Chatty Farker
Lump will flare up in the drum when it's starved for air so do not close down the vents unless you are shutting down for the night. I agree that when you opened the lid you created a back draft effect. Try using a blend of lump and briquet's with the heavy side going to the briquet's. Also you need to change or calibrate that thermometer.