I'm having the same problem. last Thursday I placed fully repaired Ant Armor, Spider Armor, and underwater gear on mannequins and a newly crafted dagger in a chest. When I went back to get them, they were all at half heath -- every item. Today I stored most of my weapons and armor in an acorn chest because I was going diving in the pond and I wouldn't need them. When I retrieved them later every item was at half health. This needs to be fixed.