The problem is that Amel was no better than other boat builders when it came to insulating cold boxes. You have two choices. You either live with it, or rip things apart and properly insulate it and end up with a box with a smaller interior volume.
A proper freezer should have, as a minimum, 4 inches of insulation. Six would be better. Most boat builders would never consider this because it makes the inside of the box look too small at the boat show. My Amel installed box has no more than 2 inches. It will sweat. The real problem is that all that condensation is wasted energy.
There is no substitute for real, effective insulation. And there is certainly no easy way to retrofit this. We live with the minimally effective insulation that came with our boat. But, every time I feel the see condensation, or feel the cold on the exterior of the box, I grit my teeth and wish for better.