Hopper doesnt work properly

I got 3 hopper on top of each other. the two bottom one are facing chest and the third on his facing down.

What I expected to happen was...:
When i put a stack of item it go on the bottom chest.

What actually happened was...:
The stack has been split in 2 stack. one in the first chest and one in the last chest

Steps to Reproduce:
1. i place a double chest.
2. i place another double chest on top of the first one
3. i place a hopper toward the first chest
4. i place another hoper toward the second double chest
5. i placed a hopper on top of the second hopper
6. i put a stack of item in the top hopper
7. everything have been split