Playing in singleplayer, I am digging a one block wide vertical tunnel downwards, and placing ladders as I go. If I try to break the block below me while I am crouching in the air, the block breaks slower than normal, as intended. If I stand on the block I am breaking, still with ladders in the same blocks as the player, the block breaks as normal, still as intended.

The bug:
In the same situation as above, if I let the player sink all the way down the tunnel so they are touching the bottom block, then crouch, the game acts as if I am airborne, therefore the block breaks slowly. On top of this, the block is immediately replaced after the breaking animation finishes, and actually breaks a few seconds after. Finally, this also interferes with the "block replacing mechanic, If I have ladders in my offhand and press both mouse buttons at once, in the intended scenarios, the ladder is instantly placed; but in the bugged scenario, I have to press my mouse again after the block breaks to place a ladder.

Tiny correction: this bug only occurs if I crouch while the block is breaking