We are having the same problem with the mold smell. It seems we had a small leak in our front bathroom shower and our livingroon sliding door, which allowed water to gather in the walls. I am still trying to find a way other than tearing down the walls to find out if mold has grown inside the walls. There is no mold spots on any of the walls, which makes it very hard to find.
I have been told to check for Black mold.