This warning category is spelled
[syntax.duplicate-ids]
by qmllint.
You used the same value for different ids .
The QML language forbids duplicate ids: they should all be unique in the same QML component.
import QtQuick Item { id: root Item { id: root } }
To fix this warning, rename the duplicate to become unique:
import QtQuick Item { id: root Item { id: notRoot } }