To reproduce:
Use this command: /setblock ~ ~ ~ double_stone_slab 10
Use your mouse wheel on the block and here's the bug.
MC-71651
Double stone slab bug
Resolved
Duplicate
0
Ulyse548
(Unassigned)
Unconfirmed
Minecraft 1.8
Retrieved
This issue is a duplicate of MC-57793. It has been linked to the original bugreport.
Please search before reporting any bugs, as it's likely that one exists already.