What I expected to happen:

When I was mining a block, I switch tools while mining without looking away from the block. The block resets to start and stars breaking again. Usally with normal blocks, you could switch tools while mining and the blocks will still be at the same point of breaking.

Steps to reproduce:

1: Generate new world.
2: Get two items.
3: Start mining a block
4: Switch tools without looking away from the block
5: It will reset back to the first point before it starts to break