Just messing with new snapshot, making an adventure map, when I was testing the new feature that lets you break special blocks {CanDestroy...

In adventure mode, when you try breaking a block, then move your pickaxe to a block you CANT break (still holding down the break button), the block that you were breaking still has the animation still stuck to it.

To try it yourself...

Be in adventure mode.
1) Get a tool using /give. For example,
[/give @p diamond_pickaxe 1 0

2) Start breaking the block (Stone in this example)

3) Move so your breaking a different block. Hold the break button down. Make sure your hitbox is touching a block, or the glitch will stop. Of course, you don't have a hitbox in adventure mode, so....

Thats it.