Unreliable block update/block falling like sand

Hi. Im a Redstoner and i do a lot of tnt cannons. this tnt cannon is shooting every 8 tick, or at least it should. it uses sand to push the tnt in every 8 tick. but i noticed that the sand is getting destroyed, which in a really older version like 1.19 or before when the mud blocks came out worked completely fine.

Info: The sand falls really unreliable. i think the main problem is when i noticed two sand are falling at the exact same time but are not getting placed at the exact same time, like 2 sand are falling in one single tick but then when they land only one of them is getting placed then the other but because there is a sand falling ontop its a bit unsync. and sand likes to fall somewhere else it even shouldnt like uncontrolable.

Ive dropped in the mcstructure of the cannon with a lever. just turn on the lever and see what happens, it is really easy to see whats going on there. sand behaves just too much like a mob or whatever

You can see how 2 sand blocks are falling in one tick but are not landing at the same tick which makes the ontop falling sandblock to unsync with below which makes it crash into the under still falling sandblock.