I have a freezer that is a couple of years old. For some reason, the water that I put in the freezer (water bottles for drinking) freeze but the ice cream doesn't freeze. It's a Frigidare Freezer (not a refrigerator) with a blower inside the freezer at the top and an horizontal slit like opening inside the freezer at the bottom. What's going on here? I have to occassionally empty the freezer and let it defrost so the ice in the bottom slit can melt.