Many automatic crafter contraptions use comparators to detect sufficient ingredients in the crafter block and send a redstone signal to activate the crafter. A contraption set up like this to craft single-ingredient recipes can break if a player closes and reopens the world while it is receiving items at a pace that is fully reliable otherwise. This applies to the simplest possible autocrafter, which consists of a hopper feeding the crafter block, and a comparator reading the crafter's fill level and powering a line of dust that points back to the crafter. This is what it looks like:

Steps to reproduce

1. Load Crafter activation relog bug.mcworld. This world consists of 8 basic auto-crafters. The crafter blocks have 8 slots locked so that they can craft single-ingredient recipes. They are disabled by power from a lever that passes from crafter to crafter through repeaters.
2. Drop a stack of bones on top of each hopper.
3. Flip the lever to enable the autocrafters. The repeaters cause each autocrafter to start one redstone tick after the one before it.
4. Observe that each autocrafter is crafting bonemeal.
5. Save and Quit.
6. Reopen the world.

Expected results

The autocrafters continue crafting.

Observed results

Some of the autocrafters break, accumulating bones in the crafting slot.