trim around ceiling cracking

Why is this happening? Our trim around the top of the ceiling/walls is cracking in half in places? It is also falling down in places. We hope someone can explain why to us. We just keep nailing it up with finishing nails{that is what is in it to hold it up}.
mamabear

How hard is it to latch you shells closed when you are closing up the TM? Do you have items left on the bed(s) that may be causing "pressure" on the roof near the edges that is loosening or cracking your molding?

Bill

no we only have a quilt laying on our bed in the back and nothing else high any were else. It is easy to lock down shell. So any other ideas. Could wheel be out of balance?
DEB