When changing the name (label) and the description of an item, save may fail with an error message, that label + description are not unique. What is done here is comparing the new label of item1 with the label of item2 and the old (!) description of item1 with the description of item2. As the description of item1 is already changed (not saved, but changed), this message is false positive.

I get the error message (sorry to lazy to find the English pendant):

Die Speicherung konnte aufgrund eines Fehlers nicht ausgeführt werden.
Das Datenobjekt Q21881507 hat bereits die Bezeichnung „Karbach“, die dem Sprachcode de zugeordnet ist, verwendet den gleichen Beschreibungstext.

Instead, the new (!) description of item1 should be compared with the description of item2.

From the user perspective I can change a lot of labels / description in one step, while the software implements this in atomic steps for each change. Combined with obviously atomic checks for uniqueness. Saving label + descriptions should check all constraints before and then save the whole bunch of changes. My workaround is something like this on item2 (!): https://www.wikidata.org/w/index.php?title=Q21881507&action=history - needless to comment on that. Change item2, save item1, undo change on item2.