Slimes, magma cubes, pufferfish, and ender dragons can consume the durability of shields within seconds

Duplicate of MC-151359

Using this ticket as parent instead.

This can be a problem when defending against magma cubes in basalt deltas. This problem is worse with MC-147694, as magma cubes don't get repelled, and continue to disintegrate the shield.

The loud sound scared me so much ._.

Confirmed for ender dragons. When flying into your shield, they damage the shield way too much.

Can confirm in 24w20a

Can confirm in 1.21.

This report may be benefited from being renamed to "Slimes, magma cubes, pufferfish, and ender dragons have no attacking delay, quickly draining the durability of shields", to clarify why this issue happens and how it would be fixed (giving these mobs appropriate delays between attacks like other mobs).

Ender dragon has a 2 tick cooldown on attack (checks when was the last time the entity was hit) but only for wings. Head attack has no cooldown so you (well, your shield) take damage 20 times / sec.

This can be easily fixed.
Minecraft 1.20.1 using Parchment mappings.

private void knockBack(List<Entity> pEntities) {
   double d0 = (this.body.getBoundingBox().minX + this.body.getBoundingBox().maxX) / 2.0D;
   double d1 = (this.body.getBoundingBox().minZ + this.body.getBoundingBox().maxZ) / 2.0D;

   for(Entity entity : pEntities) {
      if (entity instanceof LivingEntity) {
         double d2 = entity.getX() - d0;
         double d3 = entity.getZ() - d1;
         double d4 = Math.max(d2 * d2 + d3 * d3, 0.1D);
         entity.push(d2 / d4 * 4.0D, (double)0.2F, d3 / d4 * 4.0D);
         // if (!this.phaseManager.getCurrentPhase().isSitting() && ((LivingEntity)entity).getLastHurtByMobTimestamp() < entity.tickCount - 2) { original check
         if (!this.phaseManager.getCurrentPhase().isSitting() && (((LivingEntity)entity).getLastHurtByMobTimestamp() < entity.tickCount - 10 || ((LivingEntity)entity).getLastHurtByMob() != this)) {
            entity.hurt(this.damageSources().mobAttack(this), 5.0F);
            this.doEnchantDamageEffects(this, entity);
         }
      }
   }

}

As for the head damage, a new conditions must be added like the one above

private void hurt(List<Entity> pEntities) {
   for(Entity entity : pEntities) {
      // if (entity instanceof LivingEntity) { original
      if (entity instanceof LivingEntity  && (((LivingEntity)entity).getLastHurtByMobTimestamp() < entity.tickCount - 10 || ((LivingEntity)entity).getLastHurtByMob() != this)) {
         entity.hurt(this.damageSources().mobAttack(this), 10.0F);
         this.doEnchantDamageEffects(this, entity);
      }
   }

}

Can confirm in 1.21.8 (bruh)