The Bug:

If an arrow is shot from a crossbow which is enchanted with piercing towards an entity that is standing up against a wall, it is able to phase inside, or even through that wall.

How to reproduce:

1. Build a wall that is one block thick
2. Place an item frame on that wall
3. Fire a piercing crossbow at the item frame

   /give @p minecraft:crossbow[minecraft:enchantments={levels:{"quick_charge":3, "piercing":3}},minecraft:charged_projectiles=[{id:"arrow"}]]
   

Observed Results:

The arrow will either phase through the wall, or land inside of the wall depending on the angle it is shot from.

Expected Results:

The arrow would kill the item frame entity, and land against the wall.

Screenshots/Videos:

Short version: Minecraft 1.14 2019-04-24 17-23-02.mp4
Long version: https://youtu.be/05IR4RXe2GQ

Notes

Related to other piercing crossbow issues:
MC-150215 MC-158892 MC-145557 MC-270966