If there's a trapped chest in front of a hopper (the hopper points at the trapped chest) and a normal chest is right next to the trapped chest (diagonally next to the hopper), the hopper sometimes puts items into the normal chest. This seems to depend on the direction the hopper is facing and on which side the normal chest is.

What I expected to happen was...:
I expected it to put items into the chest it's pointing at.

Steps to Reproduce:
1. Place a trapped chest.
2. Place a normal chest next to it.
3. Place a hopper in front of the trapped chest, pointing at the trapped chest.
4. Put an item inside the hopper.

It wouldn't let me add an attachment, so here's a screenshot:
http://i.imgur.com/xdUEV.png