Yep, it's kind of a pain but you do need to test your oven. Fortunately, oven thermometers are pretty cheap. A pizza stone or something like that helps with temp spikes too.

Another couple of causes of vaping out weed during decarboxylation are grinding the herb too fine &/or spreading it out too thin on the foil.

Hmm just occurred to me - heavy cast iron skillets & such could serve the same purpose as a pizza stone/tiles...