Events not fired when used Windows::SetParent on QApplication

[one]

I have a similar problem but exactly opposite -
I too have a 'server' and a 'client' and I need to bring the client into the 'server's QWidget.

my code is:

winHandle = ::FindWindowA(NULL, "My Client");
        if(winHandle != NULL)
        {
            ::ShowWindow(winHandle, SW_HIDE);
 
 
            // Remove the window border
            LONG lStyle = GetWindowLong(winHandle, GWL_STYLE);
            lStyle &= ~(WS_CAPTION | WS_THICKFRAME | WS_MINIMIZE | WS_MAXIMIZE | WS_SYSMENU);
            ::SetWindowLong(winHandle, GWL_STYLE, lStyle);
 
            ::SetParent(winHandle, (HWND)(ui->widget->effectiveWinId()));
            ::SetWindowPos(winHandle, HWND_TOP, ui->widget->pos().x(), ui->widget->pos().y(), 0, 0 , SWP_NOACTIVATE | SWP_FRAMECHANGED | SWP_NOSIZE | SWP_ASYNCWINDOWPOS);
            ::UpdateWindow(winHandle);
            ::ShowWindow(winHandle, SW_SHOW);
        }

winHandle = ::FindWindowA(NULL, "My Client");
        if(winHandle != NULL)
        {
            ::ShowWindow(winHandle, SW_HIDE);


            // Remove the window border
            LONG lStyle = GetWindowLong(winHandle, GWL_STYLE);
            lStyle &= ~(WS_CAPTION | WS_THICKFRAME | WS_MINIMIZE | WS_MAXIMIZE | WS_SYSMENU);
            ::SetWindowLong(winHandle, GWL_STYLE, lStyle);

            ::SetParent(winHandle, (HWND)(ui->widget->effectiveWinId()));
            ::SetWindowPos(winHandle, HWND_TOP, ui->widget->pos().x(), ui->widget->pos().y(), 0, 0 , SWP_NOACTIVATE | SWP_FRAMECHANGED | SWP_NOSIZE | SWP_ASYNCWINDOWPOS);
            ::UpdateWindow(winHandle);
            ::ShowWindow(winHandle, SW_SHOW);
        }

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the problem I'm facing is that sometimes (not always!) the servers' buttons become not responding.
I noticed that when such a case happens, the buttons don't respond as long as they are located in the middle of the screen. but, the weirdest thing is that if i move the whole window so the buttons are located close to the edge of the screen - they work! if i move it back to the center - they stop working again.
any idea?? someone?