Why is this happening?

In september, my hubby and I moved into a brand new home as renters. In March we finally bought the home. when we first moved in, we hung up a black clay crucifix I had gotten in Mexico. It was nailed in tight to the wall, and wouldn't budge at all. He left for the day with the kids and his brother, who was living with us at the time, and the dog was with me at the apartment we had near my internship and school (I had a 2.5 hr commute otherwise). When he got home, the cross was lying in the middle of the hall in two pieces and the nail was missing. So, he glued it back together and hung it back up the same way. They all left again the next day and when they came home it was lying it 4 pieces in the hall with the nail nowhere to be found. We picked up the pieces and put them in a baggie in the cabinet until we have the time to both sit down and glue it back together the right way. Then, in April, my stepdaughter asked for a cross for her room, so I went out and bought her one.