I've been baking these chocolate chip cookies for years using the same recipe and never had a problem until now. When baking them they will flatten out to pancakes and of course make one pan size cookie. I thought that maybe the temp needed to be hotter so I tuned it up 15°F and the next batch did the same thing. I finally got out my IR gun and tested the oven and instead of being 350° like it should have been, it was only 267°. Is this the reason the cookies are flatning out like this? I attached a pic of my pancakes. I know, I need to use parchment paper, I ran out.