Lot of errors like this when loading project, and a few even before loading a project:
file:///C:/dev/qt/DesignStudio/b_qtc_PS-682rwd/qtcreator/share/qtcreator/qmldesigner/propertyEditorQmlSources/imports/HelperWidgets/Section.qml:97: ReferenceError: modelNodeBackend is not defined

Section.qml is used in many views, presumably not all of which properly set "modelNodeBackend" as context property. Either this should be fixed or Section.qml changed so that it doesn't expect the property to be defined.