There is a bug in 1.12 versions with the speed of efficiency for the blocks

This is a bug that occurs in Survival when you can insta-mine blocks, with shovel, pickaxe, sword, axe... You can play (reproduce) it mining many blocks with one of those tools and efficiency 4/5. Then, the block will be invisible, but it will be here. You can update the block putting a block in that block (site, well) or with lava or water

I wanted to leave a video explaining it with more details and, of course, a gameplay, but it has many MB (however, I leave it in Twitter for @Mojang, @Dinnerbone and @jeb_)

Please, fix it, because it's an super annoyining bug for Survival and for mine

Thanks, and good job