The bug
When you push a target block with arrows in it, the arrows remain floating as if placed on an invisible block.
To reproduce
Shoot an arrow at a target block
Move the target block with a piston
→ ✔ The arrow will move correctly along with the target blockRetract the piston
→ ❌ The arrow will not move and stay floating in the airExtend the piston again
→ ❌ The arrow is moved one block further, still stuck floating in the airRetract the piston again
→ ✔ The arrow now falls to the ground
Can confirm, the incorrect physics also apply to tridents thrown at the target block.