If you begin mining the side of a block, if you look at the top of a block while holding the button, normally the particles will begin to emit from the top of the block, as that is the side you are targeting. In older versions, block particles would always emit from the side of the block you are targeting. This is not the case in 1.21.20. For whatever reason, until you let go, the block particles won't update to emit from the face you are targeting. https://drive.google.com/file/d/14exhlqcuHoytsp-8mM034YBE6S9p8nX8/view?usp=sharing