From your recent comment about the fondant becoming “wet and humid”, I’m guessing this happens once you place the fondant onto the cake? This actually happened to me last night and I think it was because my cake was too cold (I was carving the cake and had to freeze it before carving . . . I don’t think my filling had completely de-thawed by the time I put the fondant onto my cake). Once I noticed the condensation appear, I just turned on the AC and walked away from the cake for an hour. Thankfully, didn’t have any cracks or rips in my fondant.