Sounds to me like your center section is out of round.
Because there is not a rolled lip on the bottom of the center section, it can get squished and it won't fit the charcoal bowl right. Air gets in and makes it difficult to control temps.
Check with a tape or yardstick across the diameter. It should be a consistent measurement.
My Boys: Joseph (EI); Andrew (EE); Daniel (EE)
My Toys: 10 WSMs (B, C, E, DH, DA, EZ, DZ, EO, DU, DR); 5 - 22.5" Bar-B-Q-Kettles; 2 - 18.5" Bar-B-Q-Kettle; 3 WGAs (EZ, DE, N); 2 SJPs ( DR, DR); 2 Smokey Joes (A, K); Genesis Silver C (DU); Brinkman Cimmaron; Chuckwagon Cooker; .
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