Hello,
Sorry to hear you are having issues. But, I tested and it work for me. I've test with Windows explorer and Edge. Save the group and it open properly. The only thing you will need to do is to make sure Free Download manager is properly close when you close it. Which mean you need to go to taskbar tray and exit it from there before you load the saved Groupy group. refer screenshots below.

And Free Download manager group with Edge without issue for me.

Thanks
Basj,
Stardock Community Assistant.