When mining very fast, e.g. Ice or Dirt with an Efficient V enchanted Pick or Shovel, sometimes an invisible block remains. You can't see the block, or interact with it, but it is there (eg. I can see a hole in the water surface of my ice farm, where the invisible ice block is; and I once even almost suffocated, when I tried to pass an invisible dirt block, hanging in midair, after I terraformed a hill away).
After stopping and reloading the game, the invisible block becomes visible again, and can be removed normally.
I think this bug is similiar to the "ghostblock"'s reported in the context of flying machines (but much more serious, because I want to use my mega-fast Efficient V tools).
In the bug report above, you answered, this is a client bug, not a server bug, because the block becomes visible after reloading the game. But who is responsible for developing the client, where should I send my bug report to then ?