I have a file here which was imported from MusicXML. As such, many of the instruments came across, but weren’t formally selected in Dorico. I’m working through them a few at a time as I clean up the notation and do further editing.
I’ve found that when I take one stave (player) and formally assign it to a Dorico instrument, Dorico then reorders all the tracks. It’s unpredictable, but annoying, because I already took the time to reorder the tracks in Dorico. See attached video.