First iOS deployment of our app on 5.9.3 (last deployment occurred back on 5.8 without any issue). 

Deployment done from QtCreator, and application run in debug mode on iPad Pro, until the following error occurs, causing the application to shutdown:

[...]: Type QQDialogs.FileDialog unavailable, qrc:/qt-project.org/imports/QtQuick/Dialogs/DefaultFileDialog.qml:104:31: Invalid alias target location: width).

Everything works well on desktop (macOS). 

Here is the sample code (the QML file is loaded by cpp using QQmlApplicationEngine) :

// QML file
import QtQuick 2.5
import QtQuick.Controls 2.2
import QtQuick.Dialogs 1.2

ApplicationWindow {

    FileDialog {
        id: dialog
        title: qsTr("Open...")
        folder: shortcuts.documents
    }

    Component.onCompleted: dialog.open()
}

Causing: 

FATAL 2017-11-27T21:14:44.688 (qrc:///core/CoreApplication.qml:43:5: Type FileDialog unavailable, qrc:/qt-project.org/imports/QtQuick/Dialogs/DefaultFileDialog.qml:104:31: Invalid alias target location: width)