Alton Brown and others frequently stress the importance of oven cycling temperatures, and how they should operate within a certain maximum range and how to use terra-cotta or tiles etc. to compensate for that.
I have just acquired an inexpensive remote thermometer which has a "max-min" function for testing range. I have tested with equivocal results from people opening the door and other travesties. While getting ready for another test, I would like to get some opinions for the point at which I should call a tech for a "real" test.