- 
    Bug 
- 
    Resolution: Invalid
- 
    P2: Important 
- 
    None
- 
    5.2.0 Alpha
- 
    None
This seems to only happen when the \qmlpropertygroup is declared in a qml file.
Apply the attached patch to qtquickcontrols (stable branch) and see what happens:
It won't generate the properties as group, but they will be rendered as flat "ordinary" properties, but sharing the actual documentation.