Did my first sous vide steak - and had mixed results. Set it for medium - but the result was medium in the middle with rare on one end (rare). I though this method was supposed to cook the steak (ribeye) evenly. I'm sure I did everything correctly. The only thing I can come up with is the bag. I used the one gallon zip lock bag - but form some inexplicable reason - I zipped it half closed. Could this have caused the different cooking results? Thanks