Random placed items/blocks disappear. Three items I've noticed to disappear are:
1. Redstone Torch
2. Cobblestone Half-Slab
3. Fence Gate

I notice their disappearance because they are key components of my redstone systems. Oddly enough, the halfslab and fence gate have disappeared 3x times now, and it is always the same ones. There are many cobblestone slabs/fence gates in my world, and I do not know why it these particular ones that happens to disappear (part of my villager sorter system).

Furthermore, I have 30+ villager sorter modules that are identical, and only 2x of them are affected by the disappearing fence gate.

As for the redstone torch, it is part of a pulse generator that initiates one of the phases of an automatic farm.

Attached are images of the specific items I have mentioned in this report.