During use of MP3, ACC, WAV and AIFF files recorded on a DISC it is not possible to eject the DISC by pressing eject even when the DISC is paused.

You cannot eject a DISC when a song on that DISC is being played back on the other player (a song on the same DISC is loaded to both player A and B). Pause playback on the other player or engage cue standby before pressing EJECT.