I finally found a solution which seems to work in my case. I added the Qt.MSWindowsFixedSizeDialogHint window flag, which seems to fix the issue.
So below is the modified code:
ApplicationWindow
{
// common properties
id: awMainForm
width: 602
height: 728
flags: Qt.Window | Qt.FramelessWindowHint | Qt.MSWindowsFixedSizeDialogHint
visible: true
// form content isn't relevant
...
}