bamboo raft goes into bamboo

Put the summary of the bug you're having here

What I expected to happen was...:
i put the bamboo raft on the top of the bamboo, and it should have stayed on the top of the bamboo

What actually happened was...:
the raft somehow fell down through the bamboo

Steps to Reproduce:
1. grow a tall bamboo, put the raft on top of it, leave it alone for sometime(maybe get it out of view/render distance?)
2. ...
3. ...