Good question. My first thought which you might have already checked is that you have the freezer plugged into the outlet that’s actually the “heat element” outlet, which in this setup for a keezer isn’t used. So it actually matters which of the two plugs your freezer is plugged into as one outlet is the “cooling element,” and one is for heat which we’re not using. If you’re plugged in to the heat outlet, the temp controller will correctly read the temperature inside, but as the temperature drops, it will turn on the heat element to try to raise the temperature, not knowing that it’s continuing to drop the temperature. If that isn’t the problem, then I would re-check that all of the wires are hooked up exactly as I described, as it’s easy to make a mistake there.