Over many years of smoking brisket and butts, I have concluded that fluctuations make little difference as long as you don't get into the grilling heat range and take the meat off when it is probe tender. Those thermometers can drive you crazy if you use them for any more than a general guide.
Jim - Another transplanted Texan
Former KCBS CBJ
Large and Medium Big Green Eggs , Black 18.5" WSM, Blue Weber Performer - Stainless, Green Weber OTG Kettle , Brinkmann SnP Pro, and a Stainless UDS. One retired Portable Kitchen grill.
Red Thermapen, Maverick ET-732, EdgePro Apex Sharpener.
Avatar is the original 1951 Weber Kettle