Not sure on all the start up procedures for each of the different units or what you are working with. However, I have the Classic and follow:
- Turn on, set to smoke setting, leave lid open until startup smoke is gone.
- Set to desired temperature setting and close the lid.
- I vacuum out the barrel and burn pot about every 3-4 cooks or after a long cook as there is always plenty of ash in there.
This has worked for me 100% of the time for the past 2 years. On another forum, I saw mention of cleaning the temp probe inside the barrel so as to make sure it reads correctly. I have not had an issue so I have not done that yet. Sorry, cannot help much more than that. Keep us posted if you learn more or a solution.
I have had this happen from time to time. My last cook I used a thermometer and mounted it on the grate. If I had the PB set to 250 the probe read very close to that even if the digital readout said 300. Temp swings are normal but mine mainly does it in the first hour and then levels off. Also be sure to clean off the PB temp probe from time to time.