If you load a burned CD-RW in current KDE, the drive appears to be locked by software.  Manually pressing the EJECT button has no effect.

If you then start Dolphin (to locate the mount and use right-click - eject), as Dolphin starts the drive will eject and reload without any action on your part.

If you then hit EJECT before KDE (or whatever) finishes deciding what the volume is, i.e. the device light is still flashing, the EJECT will work.  If you wait until the "Available Devices" popup appears (and the device light is dark), it will not.

If dolphin is already up when you load the disk, it is likewise locked.  Right-click and EJECT on the mounted volume will successfully eject the disk, so this looks like a software lock that is specific to CD-RW.

This does not happen with DVD +R volumes.

This behavior is fairly recent, and may have been triggered by the new kdelibs4 package to fix the open/save delays.  At least, the timeframe is suspiciously close.