It have happened to me before to a few replicas and a few genuine too. You should check the gasket on the back and lubricate it. It's probably that your watch have some water inside, maybe from washing your hands or even from your own transpirations. I always remove the back of the watch, remove the mechanism and clean the inside of the case and crystal. You can leave the mechanism in the sun, but where I live it's so humid that I prefer to close it as soon as I clean everything.
Diego