That’s strange. First, you should know that Dorico’s export to XML is not finished at all. I know, and despite its unfinished stqte, I still managed to export hundreds of pages of work, re-working them in another software to rewrite what has disappeared : tempo markings, some dynzmics (mf, mp, sfz…), accidentals, accents, playing techniques. But I never lost a player. You probably should zip uour project here for us to open it in Dorico, try the export and see what happens.
BTW, your first bar should have the time signature. Invoke shift-M popover, write 4/4,1 enter and it should look better