Once you have implemented a QSGPaintedItem, it's not trivial to decide when it's actually going to get painted on the screen. It seems that only the first one is actually painted, as you may see in this example (modified from 'qtdeclarative/examples/declarative/tutorials/extending/chapter1-basics') attached to this bug report. You can also see the code here: https://gist.github.com/e5b2a6ad6e1dc6aeff13.

In this case, we expect to see two pie-charts, one blue and other red, but you can only see the blue one. If you change the order of them, then you'll only see the red one.

There's possibly some issues when you dynamically create such elements, as I was not seeing them getting painted as well into another project.