I have an ARB 45 and an Engel 45. Both get condensation inside...mostly ice on both sides of the cooling element.
This is mainly due to the humid conditions I'm usually camping in. I started getting this from day 1 with my ARB (bought it new).
I wouldn't worry about it, but when you go to turn it off, make sure you wipe out what you can and then either prop the lid open or take the lid off to let it dry out.
Also, pull the green mat from the bottom and dry it out. I usually pull it and place it sideways in the basket so that it won't trap water underneath.
Last year when I camped in AZ, practically no condensation inside. I really think it has to do with how many times you open it and how humid the environment is.
If you pull a beer out of the fridge and it begins to create condensation on the bottle, then you should expect the same inside the fridge each time you open it.