You probably have the sticky field option toggled on for the first field, which will cause Anki to warn you immediately after adding a note, because as the content of the field didn’t change, it’s now identical to a note you just added.
You probably have the sticky field option toggled on for the first field, which will cause Anki to warn you immediately after adding a note, because as the content of the field didn’t change, it’s now identical to a note you just added.