If you try to place lave in a waterloggable block by using a lava bucket the lava in the bucket just disappears. You have to do this by placing it on the side of the block next to it or at the top of the block below or at the bottom of the block above. Does not work with all waterloggable blocks. If you look at the waterloggable block it works finde. 

How to reproduce:

1. Be in survival mode.
2. Have a lava bucket. 
3. Place a fence on top of a block. 
4. Look at the top side of the block with a fence. 
5. Try to place the lava with the bucket. 

What I observed: The lava disappeared.

What I expected: Nothing happens. 

I have attached a screenshot where you see all of the blocks that I found out that it works. I also have attached a video where you see this bug in action.