It is one of two things 1) Your Charcoal has drawn damp and wont hold a fire or 2) Your basket is to close to the bottom of the drum not allowing enough air. it need to be at least 3" off the bottom.
So cooking chicken at 210 how did you like the rubbery skin? My UDS don't run below 250 & more in the 275-350 range. Poultry being in the upper end of that 325-350. Food for thought.
I never met a Cow that I didn't like with a little Salt & Pepper! Certified PORK-A-HOLIC