When using snapshot 17w13a pistons don't appear to animate correctly, instead the seem to just switch between retracted and extended.
Example of what I'm talking about: https://gfycat.com/AnguishedFaroffBunny
MC-114887
Pistons don't animate properly
Resolved
Duplicate
16
Riley Chase
(Unassigned)
Confirmed
animation, block, piston, piston_head, redstone
Minecraft 17w13a
Retrieved
Most likely MC-114881, moving pistons are block entities.