Inherited custom properties can't be copied

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The goal ist to build up a folder hierarchy (incl. the defined custom properties) within the documents space. After having a dummy element defined and assigning the right “custom properties” elements to the appropriate level (important because of inheritance), this dummy element would serve after renaming as basis for all future elements.

Unfortunately, after copying it, it seems, that only a couple of custom properties were taken over properly while the others are simply listed above the “Custom Properties at other levels” line, instead of belonging to the right level and fulfilling their inheritance goals.

Is there anything we have to fix in order to achive our goals?