Your temp variation is typical of PID controlled units. They are balancing ambient temp, speed of pellets burning, speed of pellets being dropped, speed of fan, amount of heat output by burning pellets, etc. And then you open the lid or crank up the temp setting........
I always run an air probe to see what is going on. You will find that the controller temp shown (determined by the PID) is generally 20-50 degrees higher than the air probe temp. This is to keep from burning things up. The SF controller/PID does fairly good at 200-225. From 250-375, it gets a little flakier. At 400 and above, it is working fairly well. IF any changes are made to any of the input factors above, the PID is playing catch up and fighting against its programing and the input it has been receiving from the temp sensor.