I have three WSMs. None of the doors fit perfectly. There is always a small leak but it can be compensated for by adjusting the intake valves. If I want to cook at 225 and I never do I fill the water pan and maybe just crack the intake valves.
The only time I have had with temp spiking is when I didn't have the top on completely. On one cooker the middle section got out of round and it didn't seal. I fiddled with it though and now with a little pressure the top will fit properly.