When I attach a Fence Gate to a Sticky Piston and pull the lever the sticky piston and fence gate vanish for a second and come back. Also, when the piston pull it in, the fence gate turns into a "Missing Texture" but then returns to normal.
I also noticed that the piston and block both vanish when the block is not a full block. (e.g. fence,rail,gate)

Thanks for reading,
Powerman800