Thanks! I actually searched for related things but not well enough since I didn't it.

That actually does seem to be related in the exact opposite relation, because it works if copy/pasted but not if placed manually.

That inserter works if copy and pasted. It also works if the chest is hand placed ...

What did you do?
Place an inserter to remove items from a cargo wagon on a curve.

What happened?
The inserter indicated with the extra outline on the cargo wagon that it will interact with it, but does not insert or remove.

What did you expect to happen instead? It might be obvious to you ...