If you dig ANYTHING and then walk out of range while still holding down right click the digging animation is still there. If you then walk up to the block and as long as you look in air you can look at it. If you then look at the block again you can continue to dig it at the state you left it. Note: you have to hold won right click all the time. And dont just watch at the side, you must walk out of digging range of the block to reproduce the bug.