changing Motion:[X, Y, Z] tag on projectiles don't change the motion only server side, resulting in the projectile visually teleporting regularly on previous locations, or not moving at all. this is problematic for datapacks makers when you want to do a weapon that throw custom projectiles, you have to change the motion of the projectile after summoning it with a /data store entity

step to reproduce:

summon a falling_sand with no motion, then change it to something else, visually it will fall right down, but when hitting the ground the sand block will teleport onto the location where it really landed.

probably related to MC-128812