I'm aware of bug
QTBUG-30467 wich affects the use of modules over a network connection. This bug might be related but I'm not sure how.
When loading an QML-Type over network this type might import a different namespace and in that namespace declares a singleton. So far everything works as expected. But this singleton might inherit a user defined type. This leads to an empty qml view. No error is displayed though.
See the attached zip file with a working reproducer. You need to serve the folder via http for example by using the command python3 -m http.server.