"Left" key not working in Neo layout

In the Neo layout: http://www.neo-layout.org/, a "left" keypress is generated when pressing "Alt Gr" + "s" or "<>/" + "s". This worked fine for the older qtcreator.

Since 2.8.0, however, pressing "Alt Gr" + "s" does nothing in the editor window. When keeping "Alt Gr" pressed, and pressing "s" a second time, then it works. For the "<>/" + "s" combination it still works as expected.

I first assumed it might be a qt5 problem, but when creating a very simple qt project and doing something like this:
void MainWindow::keyPressEvent(QKeyEvent* event)

I get the same key (16777234) when I press "left", "Alt Gr" + "s" or "<>/" + "s". However, it is preceded with an event "0" when "Alt Gr" or "<>/" is pressed first.

Is qtcreator somehow mapping the "Alt gr" key to something else?

Can I provide any more informations?

Update:
I just checked: When downgrading qtcreator the same problem occurs still. So it must be somehow related to qt5 after all...

Update2:
Also, when starting qtcreator with the neo layout enabled, I get this error message:
Error: Key "<MDSW>" added to modifier map for multiple modifiers; Using Mod3, ignoring Mod5
This doesn't happen with the english layout, but I don't know if its related

Update3:
Running the mentioned example above with qt4, I get a code of "-1" instead of "0" for "Alt Gr" and "<>/"... qtcreator might handle this codes differently