Exploding kombucha?

Fermented drinks produce carbon dioxide and therefore pressure inside closed containers. Thats just how it works. Combine that with freezing temps, ever so slightly, and a disaster is bound to happen.
Sure enough.... we lost a few bottles of kombucha in our new coolers. They started freezing and that was just too much pressure inside the bottles. The quart mason jars just spewed liquid all over the inside while the single serving bottles cracked and sprayed a few glass fragments. Either way.... a mess
It is a bit more challenging to set the thermostats on these units. They are old capillary based design without a defroster. Instead of a defrost timer that turns on a heater or at least locks out the compressor to defrost the inside coils, these units work on differential. The thermostat has a wide differential where it cuts on about 15 degrees higher than it cuts off. So something like on at 40, off at 25 degrees. The time between 32 and 40 while off allows the defrosting. The food stays at an average temp of about 32 with these settings since food has more mass than air. It all works quite well... but for periods of time the air is below 32. It also makes it tough to set the temp by an air thermometer.
Instead, I put in a half gallon jar filled with water to simulate a milk jar. Then put the probe of a remote read thermometer into the water. That tells the temp that the water stays over time, much easier to set the thermostat to without loosing more frozen jars.
So... now one is set at 34 and the other at 38. That one needs a thermostat replacement to get lower. There is no ice inside now and no more frozen bottles. There is, however, a nice aroma of kombucha vinegar when you step into the store!