The spike in temperature was definitely caused by the wood catching on fire. Dry wood ignites easily. The other thing I would note is that you don't need foil for the seasoning smoke ... leave everything bare so the oils (machine oil?) burn off and you will get a nice seasoning color on all sides/floor of the unit. Also, no need to monitor the box temp when there is no meat in the box...you will see all kinds of temps!
I do periodically monitor the box temp when smoking certain meats, just to see the range of temp swings. Not really necessary, but a temp probe for the meat is essential! (Also, you will want to use foil for the bottom and wood box when you are smoking meat!)
When you try the seasoning again, don't use foil on the floor/wood box, and don't use a temp probe. You can try foiling the wood, but if it is really dry, then you will probably see the heavy smoke and "the belch" when the wood ignites. Just let it go for the duration, and you will be set.
Good luck!