App with a QWebEngine widget does not scale on High DPI

On Windows 10, if you have 2 screens, one with a High DPI, another with a normal resolution, an application with a WebEngine widget (in a UI file), will not scale appropriately when dragging the application from the High DPI screen to the normal resolution screen.

To reproduce it, use the MarkdownEditor of the WebEngineWidgets example.

See in the attachment, the black line between the frame of the application and the header. This is not only a visual problem: their is a discrepancy between the pointer and the UI widgets, e.g. you cannot click on the File menu easily.

This problem does not seem to occur when the WebEngine is in a QML application.