Answer to

The robotic always tries to unload a CD/DVD from a recorder which has no media?

The drives are not correct assigned. Follow this procedure to re-assign the drives in the right order:

Under Configurationsettingsdevice configurationsetup you can mark each drive and "remove" them all.

Starting with Device 0, please re-assign ( use the "add" button ) the drives in the same order as they are installed in the system ( check by using the "Test" button ).