Absolutely not! In fact, I don't think I've ever seen flan come out of the pan with every last bit of caramel liquified. My mother-in-law, from Brazil, showed me a great method for getting the extra caramel out: Add a splash of hot water to the stuck caramel in the pan. Let it sit for a few minutes, then stir, pressing firmly on the caramel, with a rubber spatula. Repeat, adding more water if the caramel gets a bit too thick until the caramel is completely dissolved into the water. Pour over your flan and enjoy!