A Bad Smart Item can irreversibly break a scene

[nearnshaw]

If a smart item has a badly constructed composite.json, adding it to the scene can completely break it, and there's no way to bring the scene back to life (except maybe manually editing the scene's composite.json)

20250307-1924-53.7640811.mp4

It's unclear what kinds of problems in a smart item can break a scene like this.

The following items are very similar, but one works fine and the other doesn't.

This one works fine:

rising_pillar_temple.zip

This other one, very similar, breaks your scene.

rising_pillar_pirates.zip

You can easily test these by adding them to your Custom Items folder, and use them from there.
Warning: try it in a scene that you won't mind breaking. You won't be able to recover it.

If in the broken item I change the field isBasicViewEnabled to false, it works well. That is until via the UI I activate the basic mode. Then it breaks just like when I add the item. So the problem is clearly related to the basic mode.

The problem is also surely related to the fact that the first item (that works) has a single entity, but the second one (that breaks) has two nested entities. Perhaps related to the fact that the component for the basic configuration is added to the parent, but it references components that are present in the child. This explanation makes sense, but I also tried a lot of variations and it keeps breaking. Including adding the basic-configuration component to the child entity, etc, and it still breaks.
TLDR, the exact problem with this item is still a mystery.