The bug:
When a crate is filling up completely, trying to transfer items into it (using Integrated Tunnels) frequently fails due to inconsistent insertion behaviour with the crates. Integrated Tunnels dev says there are two modes for item insertion, simulated and real. The error occurs when there is a conflict between the two. So essentially the crates are "lying" how much items can be inserted.

How to reproduce:

1. Place a crate
2. Place a Logic Cable next to it
3. Attach an Item Interface between crate and cable
4. Place a machine next to the cable (that produces the item desired)
5. Attach an Item Importer between the cable and the machine
6. Insert a blank Variable Card into the importer (top aspect, default properties)
7. Let the system fill up the crate
   ❌ when the crate is about to fill up 100%, the importer will error out and spew out items if they cannot re-enter the machine

This applies to machines that don't allow their output to be re-inserted back into them, such as Mystical Agriculture's Ultimate Furnace (it has strict I/O). For less strict machines such as Cyclic's Auto Crafter, the overflowing items are re-inserted back into the machine, blocking their process. However, Item Importers are only supposed to pull items, not insert. It is a form of error handling due to the crate not handling input correctly.

Version: 0.0.24
Integrated Tunnels: 1.12.2-1.6.11
Integrated Dynamics: 1.12.2-1.1.6

Caused by this problem, it is not possible to use crates as an intermediate storage bottleneck between two systems, as the previous system that runs into it will get blocked by the inconsistent behaviour.