I'm baking a Trader Joe's ready-made brownie mix (i.e. you add nothing, just open the bag of ready-made banner, pour into an 8x8 pan and bake). Instructions: bake 22 min @ 350. Currently: we're up to 35 min and the middle of the brownie mix is still swampy but the edges are just starting to come together.
Question: why? Is this an indication of a dramatically under-heated oven? (Sadly, don't have an oven thermometer to verify.)