Yes, when you import a MusicXML file into an existing project, choosing to use existing players where possible will not force the incoming music into the players that already exist: it will only use those players if they match the ones that Dorico works out it needs from the MusicXML file. And in any case you cannot import directly into an existing flow: it will always create a new flow.
Hello Daniel
Thanks for your answer
How can I help my XML or Midi instruments to Match with Dorico’s one ?
How can I avoid this dead loop ? (see primary message)
Can I merge the flows ?
Thanks
Best
You cannot merge flows, except by copying and pasting the music from one to the other.
Dorico does not in general crash when changing instrument, so if you have a reproducible case, please zip it up and attach it here so we can take a look.
What happens when you use Dorico’s File > Import > MusicXML, the key equivalent for which on a Mac is Shift + Cmnd + O, so presumably Shift + CTRL + O on Windows, to import the XML file into an otherwise empty document?