What do you mean with “stems”?
I had a similar experience:
Yesterday I tried to export my score and it’s 10 layouts as PDF files. I went to Print Mode and selected all layouts at the left. Print Mode opens at default with the Printer (on the right). At Page Setup Paper size “US Letter” is been displayed. I change it to “DIN A4” - because this is the standard paper size, we use here (Dorico does not respect it’s own Preferences - Default paper size type “International”). This step might be unnecessary, because I am not actually print the layouts now, instead exporting them as PDF files. Anyway, because I change 10 layouts at the same time, Dorico gets very busy - probably because it has to recalculate the Print Preview - and eventually stalls. Like yesterday the file became unresponsive. I did an emergency Cmd-S which seemed to have worked, but I could not close the program window or quit Dorico. I had to force quit/kill the application. After reopening I noticed that the last Cmd-S did not trigger a Save, as I was working on an earlier version from the last real Save.