Pickaxes with high level of efficiency enchantment will causes item blocks like netherracks to instantly break. and when you breaks a lot (spamming), it suppose to break really really fast and create a path for you to walk.

What actually happened was...:
It happened so fast that I assume that the system did not register the blocks being broke and remained there as an invisible block. when you walk into it, it will suffocate the player.

Steps to Reproduce:
1. Get Efficiency IV or higher on iron or diamond pickaxe
2. Destroy netherrack while walking toward
3. Sometimes it blocks you, and sometimes it suffocate you
4. The invisible block reappear if quit the game and join it again.