I've noticed this issue since UP8.
2/3 boot ups, I notice any attached optical drives will have issues. That is, the discs won't be mounted and the drives are detected as empty even if there are disks in the drive. It happens when logging in for the first time after a power on or reboot or if changing the disks in the drive. You can eject the media either by physical eject button or right clicking the optical drive and selecting eject. The device always appears as empty.
To make the devices "suddenly work", you need to run fdisk -l. Suddenly the devices become alive, the discs are detected, are auto-mounted, and caja pops up showing the disks contents. eject the disk and replace it with another disk, and you must run fdisk -l again to see the new disks.
When I tested the issue, I noticed that out of 3 cold reboots, 1 out of 3, the drives would be working as expected without needing to run fdisk -l to detect media.
I'm able to reproduce the issue on both a 32bit and 64bit system, with 1 system having 1 optical drive, and the other system having 3.