Mobs picking up items they shouldn't be able to and not dropping them when killed

As described in the summary, it appears that mobs are picking up items that they should not be able to when they are left on the ground after dying and then not dropping them when they are killed.

Specific scenario:

Die to a baby drowned at the end of an underground cavern. No other mobs around.

Return to the location in under one minute because respawn location was close by.

Find the baby drowned that killed me, and see that it is wearing most, but not all, of my armor. It was wearing my pants, helmet, and boots, holding my shield and sword.

No other items were on the ground, and no other mobs either.

List of items that were/should have been dropped on death include:

• Ender chest

• Enchanted bow

• Multiple shulker boxes

• Multiple stacks of various blocks

• Multiple stacks of items (Food, arrows, mob drops, etc)

• Elytra

None of these items existed. The only conclusion that I can make from this is that somehow the one and only mob that was in the area picked up literally every single item that was in my inventory but then failed to drop those items when it was killed. This is a major bug, and I have no idea how this could possibly have gotten by anybody there, but it needs to be fixed as a top priority issue. There is absolutely no point in having items have any persistence beyond death with this in play. As it stands, if you die, it is physically impossible to retrieve your items at all.