Stuck in CreateWindowEx

Hi,

My application became stuck in CreateWindowEx().

Here is the scenario:
1. One Qt process sends a WId to a child process
2. The child process tries to embed a widget into the parent window.
3. When we call `show()` on the widget, it calls to CreateWindowEx() which becomes never returns.

To reproduce it, you can checkout the repository: https://github.com/free-audio/clap-examples and run the cmake target run-host, then you can attach clap-gui.exe.
The same code works perfectly on X11.

Thank you very much!
Alex.