The bug

Arrows shot by skeletons and tridents thrown by Drowned (in the snapshots) cannot be picked up by players in either Creative or Survival mode. This is inconsistent with arrows shot by players with an Infinity bow or in Creative mode, which cannot be picked up by Survival players but can be picked up by Creative players.

How to reproduce

In the snapshots

• Spawn skeletons or trident-holding drowned with

   /summon drowned ~ ~ ~ {HandItems:[{id:"trident",Count:1}]} 

• Spawn baby turtles to cause the skeletons/drowned to aim at them
• Attempt to pick up the arrows/trident in Creative mode

In 1.12.2

Spawn some skeletons, then switch to survival mode and attempt to make the skeletons miss while shooting at you (Easy difficulty may help since it worsens their aim). Switch back to Creative and attempt to pick up the skeletons' arrows.