It's hard to say, because moving them can cause that, but you'd probably notice it when you moved the cake.
That could happen if your cake board isn't solid/strong enough and it didn't support your cake well while moving it. That may explain your cake boards appearance....I don't like the sag look of your paper around the base of your cake. It looks like your cake board is too thin and the paper soaked up some humidity through the paper covering it, and compromised the cardboard cake circle it's sitting on.
Otherwise it's would happen from the weight of your cake settling downward while your frosting layer was strong and tried to remain firm.