If a qml module has a mix of Rectangle and Button derived qml types, deleting qmldir file and then undoing that file delete after the types have been invalidated in qds, not all types will be restored properly. E.g. see the attached project and its Generated.Bundles.User2D module:

• Open the project
• Delete Generated/Bundles/User2D/qmldir file
• Wait until relevant nodes in navigator show a warning triangle as the types are invalidated
• Undo qmldir file delete

--> Not all of the Button derived types are restored to functionality. They still show the warning triangle in navigator and if selected, properties are not shown in properties view.

Saving the project will fix the issue.