Arrows or tridents (currently invisible in beta 1.12.0.2) fall into the ground after blocked by a shield, tested this with pillagers in raids but not tested with drowned yet.

To reproduce
1. Get shield
2. Spawn mobs that can shoot arrows, drowned with tridents or use dispensers

Observed Results
Arrows or tridents shot from certain entities or dispensers fall into the groud when blocked by a shield.

Expected Results
Arrows or tridents shot from cerain entites or dispansers shouldn't fall into the ground when blocked by a shield. It should land into the surface of the block.