This bug occurs when you try to place an armor stand(with the armor stand item) on top of a block that has items on it. This bug could be in versions prior to 1.10.2, but I didn't test earlier versions. The bug is that when you try to place an armor stand(item) on a block with items also on it, the armor stand just won't place.
Linked issues
Comments 5
Dupe of MC-89178 (was resolved but wasn't linked)
What happens when you place the armor stand, and what were you expecting to happen?