Exception: Delete a staging "box" which was previsouly copied from another site in another lang

Use case:
I imported the ACME site (not published yet). I created a new fresh virtual site based on the web-blue-template but in DE lang only. Then on the home, with root, I tried to copy the "How to use this demonstration?" boxlet available on the home of my ACME site at the exact same position in the newly created DE site.

I did the first copy without activating the area. I did a second copy, at the "list: how-to-use-this-demonstration" level, with the area activated. Finally I deleted the whole list (in fact nothing appears as the lang is not the same excepted it displays an empty list named with the same id from the original list).

When deleteing the whole I got this serie of exceptions (in attachment)