Affects Version/s: Minecraft 14w27a
Fix Version/s: None
I decided to make a small table to do the new potion of leaping. When I placed a source of redstone power and then placed the piston, it's head simply disappeared.
When I tried placing the piston first and then added the redstone power, it worked as intended, as you can see on Screenshot_2 and Screenshot_3.
Screenshots are attached showing the bug.
EDIT: Forgot to add some pictures relating to the piston placed sideways and up/down.