I am still trying to work this issue out with my (wine fridge) cave also. What I found out is that my caves cooling coils are behind the back wall. When the compressor is on, the back wall cools and condensates the humidity on the wall. It then collects and runs down the back wall and is guided into a hole that goes outside the cooler and into a pan near the compressor where the heat from the compressor evaporates the water. What I have done (that has helped a lot), is to plug that hole in the bottom back of the cooler. I have not gotten the RH exactly where I want it yet, but plugging that hole (to keep the water in the cooler) has made a huge improvement. You might want to take a look at your cooler and see if it operates the same way.