I can't help you directly, except to inform you that this has never happened with ours. So it doesn't sound normal to me. But I've also never listened to music on the side for a longer period of time without doing something on the pc (afk, so to speak), I have to say. Maybe a firmware upgrade could help, have a look at de.jbl.com/gaming-speakers/QUANTUM+DUO-.html under documents+downloads.
Unfortunately, we currently have no information on when the item will be available and when we will be able to deliver it. As soon as something changes in this regard, we will post it here. Sorry.