AVP17 has to detect many data formats, and whenever there is a long digital signal lapse, it will re-detect the the incoming signal. Newer CD players and DVD players usually will not send out such digital nulls between tracks to prevent the downstream equipment from re-detecting (or re-syncing).
During the re-detection, the AVP17 scrolls and shows the detected signal format, eg, 'PCM 44.1kHz'. If the display scrolls this message on every track, it's doing the re-detection. Otherwise, after the message 'PCM 44.1kHz' first scrolled up, the display just maintains a static display of (eg) 'DVD Coaxial' on subsequent tracks.