Well, most likely it is condensation on the board. The gyros are working normally from what I can see.
Depending on what kind of insulation you use for the box, it can suck up quite a lot of moisture from the air.
Try and dry out the box, insulation and board before putting them in the freezer. This time of year, it is easy to get condensation.
When I get this problem, I place mine on my woodfired stove and let it dry out at 60C for an hour or two before freezing it. Do not go above 80 degrees!!! If your kitchen-oven can do low temp, it might be a good candidate. Otherwise, just place the open box on a radiator or similar and let it dry out there.
When you place the box into the freezer, you can just leave the lid open but set at an angle. This will allow the contents to come down in temp, but protect from moisture getting inside. Look at attached photos.
Leave the top insulation in place:
And put the lid on a angle before placing it into freezer: