When the first song, the song from Spain, was to be started, the sound technicians forgot to turn the sound of the pre-recorded backing track on for the orchestra director. The pre-recorded track contained only certain music elements and rhythms that the orchestra couldn't reproduce live. This resulted in a half a minute silence while the orchestra director waited still for the signal from his headphones to arrive, so that he could synchronize the orchestra with the recorded track.
When techs discovered the error, instead of rewinding the tape, they simply turned the sound on mid-way through, which made it impossible for the director to synchronize the orchestra with it. It also caused the problem that the singers arrived late to the microphones, as the song started for them later than it should and they were doing their rehearsed choreography, not to mention that the music was incomplete without the orchestra instruments.
The chaos was such that the singers simply walked off stage and waited backstage for the problem to be fixed. The backing track kept on being played yet for another minute, while the Spanish musicians in the background were awkwardly dancing to their own prerecorded instruments in front of the live audience. Finally, after a long minute, the music was turned off, they rewound the tape, and the song was properly restarted.