quicknanobrowser's popup window can't be moved or closed

1. Open a Release page at junodownload.
2. Click on one of the small "CUE" buttons.
   A new window with an audio played opens.
   That window stays on top of everything else, including other applications and can't be moved. It doesn't have controls for closing it, either. It can only be closed using Windows' task bar.

It should be possible to move this window, send it to the background and close it. It works fine in Firefox 104.