That's odd... I've had my Metcons since March and haven't experienced that at all. The only issue I had at first was slight heel lift, but after a couple of weeks the broke in and I don't have that issue anymore.
By no means do I mean any disrespect by this, but I've been doing crossfit for 4 years now and whenever I hear of anyone complaining about their feet pushing forward during a Thruster or KB swing it is usually a form issue. As you are doing these movements are your heels planted firmly to the floor and do you have the ability to wiggle your toes freely during the movement?
Many times you see people struggling in the front rack position because they don't have the mobility to hold the bar properly during the front squat and it causes them lean forward and their heels to come up which is going to push your foot forward. Same with KB swings, so many people have a tendency to lift their heels up and go onto their toes rather than drive their heels into the floor and explode from their hips to push the KB up and through the window, which again is going to cause your foot to move in the shoe.
But, everyone has a different shape to their foot and the arch, width, bones, old injuries, etc... can cause various issues with equipment. Just wanted to toss that out there just incase.