Entities with PhongAlphaMaterial disappear when there are several of them

There was QTBUG-53935 bug - when entities with PhongAlphaMaterial are not worked within Scene3D. It somehow got fixed with recent commits to 5.7.

I hoped that another problem (the one in the title) would be fixed with QTBUG-53935 too, but unfortunatly it still exist.
I wrote about it in qt interest mailist http://lists.qt-project.org/pipermail/interest/2016-May/022352.html and made video demonstation https://www.youtube.com/watch?v=InxhSB_YuhU

Now I make small example for tests: 3d scene root entity is in Scene3D item, that is in Loader Item within QML application.
In the scene there are SkyBox entity and Ground entity (a plane mesh). Also there are first "path piece" (a small plane mesh) with PhongMaterial and path piece with PhongAlphaMaterial with Alpha = 1.0f
Then by timer PhongAlphaMaterial path pieces with Alpha = 0.3f are added to the scene.

After about 12 path pieces every path with PhongAlphaMaterial (even with 1.0f) disappear, the first one with PhongMaterial is shown.

If not add SkyBox or Ground to the scene, that is comment one or both of this:

    m_skyBox->setParent(this);
    m_ground->setParent(this);

there will be some strange behaviour, for example first path piece sometimes got rendered on top of some the new pieces.

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Another thing I've done before that, I modified bigscene-cpp so that it is QML application, with Loader Item, with Scene3D item and 3d scene root entity and it works: