You need to check the bowl, the middle section, and the dome to see if anything is out of round.
I just picked up a WSM with an out of round bowl and center section. Once you find where the out of round is, a good gentle bear-hug will get things back in order.
If your bowl is out of round at the lip, the middle section will not fit right - air leak.
If the botoom of the middle section is out of round, it will not sit on the bowl tight - air leak.
If the top of the middle section is out of round, the dome will not fit right - air leak.
As far as the door goes, it may be a little mis-shapen. But, if the latch is not pulling the door closed all the way, you can tweak the door all you want and it won't seal.
I have 8 WSMs. All have stock doors. All have been checked for out of round. All maintain great temps. The fire snuffs in all of them when the vents are closed. If your WSM does those things, but a little smoke sneaks past the door, get over it.
My Boys: Joseph (EI); Andrew (EE); Daniel (EE)
My Toys: 10 WSMs (B, C, DH, DA, EZ, DZ, EO, DU, DR, EE/DU mutt); Brinkman Cimmaron; Chuckwagon Cooker; 4 22.5" Bar-B-Q-Kettles; 2 18.5" Bar-B-Q-Kettle; 1 Red OTS (H); 3 WGAs (EZ, DE, N); 3 SJPs (DT, DR, DR); 2 Smokey Joes (A, K); Genesis Silver C (DU).
"For when democracy becomes tyranny, those of us with rifles still get to vote"