When trying to "eject" mounted DVD by right-clicking on its icon and choosing "eject", it refuses, complaining: "Failed to eject medium; one or more volumes on the medium are busy". Well, the volumes AREN'T busy - at least I didn't run any application, which would be using them. So next is the attempt to unmount it from the "File Manager" view (when showing its contents), by right clicking the CD icon from the list on the left (after "opening" the CD): now it's asking, whether "Unmount anyway", because "one or more applications are keeping the volume busy" - and in the list shown in window below there is "thumblerd".

After forcing the ejection by clicking "Unmount anyway" it returns the CD at last, opening the drive door - the problem is, that after such forced eject, once the drive has been shut, it won't open again by pressing its button (I mean the one on the drive box, not talking about clicking any icons/buttons on the screen). And because /dev/cdrom vanishes somehow (removed by thunard maybe?), there's no other way to make CD open again, than by restarting XFCE. It seems, that it's blocking CD-drive somehow after such forced unmounting.

Very similar problem I noticed with several USB-sticks: it fails to "eject", complaining "Failed to eject medium; one or more volumes on the medium are busy". The same procedure, as described above, allows to force unmount it anyway. This error doesn't happen with every pendrive - but there are sticks somehow "disliked" by Tumblerd. With these it happens all the time.