Something wrong with this XML?

I modified the attached Dorico file to export it as XML and upload to Cantamus. It was previously done as divisi, and I created a second instrument and got rid of the divisi.
I Will Sing with the Spirit_AUDIO.dorico (726.0 KB)

Problem: when I import it into Cantamus, the Voice 1 playback gets delayed by one beat: the pickup is together, but it inserts a beat of rests on the first downbeat, shifting the rest of the track off by one beat. Also, the import displays like this, with odd rests in voice 1 that aren’t present in the Dorico file that I can see:

Is there anything hidden in the XML export or in the Dorico file itself that might be causing this? I’m really keen to get this working, and to try to learn the particulars of how Dorico’s XML export plays well with other programs.

EDIT: I imported this XML into Finale. I still got the rests in the downstem voice, but the playback was ok (the two voice parts lined up).

The rests (Part I, voice 2) definitely exist in the xml. That aside, the xml imports correctly to MuseScore (my ‘go to’ for questionable xml files) and plays back correctly. My guess would be that Cantamus has a problem with pickup bars. What happens if you make the meter explicit for the pickup bar?

The issue is that because you previously had divisi in the first instrument, there’s an extra voice that ends up assigned to that first instrument. Create a new first soprano instrument and copy and paste the music from your original instrument to the new one, delete the original one, and then re-export your MusicXML file.

Thank you. That makes sense. I’m assuming that voice also accounts for the offset in playback, since there’s probably something about how the extra voice is interacting with the quarter note pickup.

I have only a few more free uploads remaining on the trial, so I’m not going to test this particular file any further, but I will keep track of how things go in case other users want to try utilizing this software direct from Dorico.