I've also created a 32 bar song with 20 repeats. I'm not sure, but maybe the song is still generating in the background if you:
1: Generate and Play, then
2: Press Stop before the background generation has finished, then
3: Press Play.

I tried Song Settings > 'This song has playback problems disable fast generation', and generated and it then took a very long time to generate the song (2+ minutes). After that, pressing play took several seconds, but much less time.

So it may not have completed generating the song, and pressing Play still requires the song to regenerate.

20 choruses = around 23 minutes of music.

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