Hi Philip,
OK, I see what you are experiencing.
If it plays SACD sometimes, you have the right physical connections and settings.
If the Delius loses contact with the Verdi during playback, then displays "Search", it seems likely that the physical connection has an intermittent fault such as a loose joint in the 1394 cable, or one of the sockets.
I would try a different 1394 cable to eliminate that. If it's in the machine's internal connections you are obviously looking at dealer/manufacturer service.
I haven't anything similar with mine - it has never lost contact with a source after it has locked on.
Can anyone else shed some light on this?