Temp swings are perfectly normal, I see them all the time...sometimes small, sometimes a bit larger. In the end, they average out at your desired temp, so no worries!
Phil - the best way to deal with temp swings on the stock analog controller is to stop monitoring box temp! Set your desired temp, and walk away until you hit the right internal meat temp. Easy peasy. The only way to get tighter temps is to use the Auber PID controller. It's certainly not required to make great Q, but will add a little more control and consistency on temps.
Thanks guy's smoked 2 racks of baby backs set it at 235 no peek, well after 4 1/2 hours I looked !! got some bark closed the door for 1 more hour turned out great thanks again, I'm a big green egg guy, but this smokin it sure is easy and they turned out great !!!