The set up is a walk-in ref and freezer sharring a common wall. You walk through the ref to get to the freezer. The common wall is the door wall. On one side of the common wall away from the door is a round spot that just seems to frost on the wall for no reason. If you chip the frost off it grows back slowly but it grows back. This spot is away from the outer wall but is located on a seam where the panels are locked together. it's just odd.

Any thoughts.