I was cutting down a tree, i nearly finshed breaking a block of wood with some wood in my hand then i switched to an empty slot in my hotbar and it reset the entire breaking process and i had to recut down the wood, its easy to reproduce just cut down a tree with a single block of wood in your hand, then switch from that wood to an empty slot during breaking a block and you will see what what i mean
Actually the behavior you describe is duplicate of MC-2519 which is intended.