If you try to edit both the label and the description of an item simultaneously, and there is an item which has the new label but the old description, it gives an error.
To reproduce it:
create an item with label "some label" and description "some description" (which I did at https://test.wikidata.org/wiki/Q1458)
create another item with no label and description "some description" (which I did at https://test.wikidata.org/wiki/Q1459)
edit the second one, set the label to "some label" and the description to "some other description"
try to save
Expected result: It saves the changes, because the new label and new description are unique.
Actual result: It gives an error on the label field because the new label and the old description are not unique. The error message is:
An error occurred while saving. Your changes could not be completed.
Details
Item some string (Q1458) already has label "some string" associated with language code en, using the same description text.
I did find T76703 but that doesn't seem to be the same. I haven't edited the description first and tried to edit the label separately after that, I'm editing both simultaneously.