I am having this sort of problem (at measure 10 ) of the attached. The original file was imported as XML from Finale into a very early version of Dorico and has been updated as Dorico added additional capabilities. I cannot seem to get rid of the Tenor-G clef in the lower voice where the Divisi starts.
I tried changing the instrument in the player to see if that was the problem, but the Change Instrument pull-down command in Setup did not bring up a panel to do so.
No, unfortunately this is the kind of problem that still exists. In this particular instance you should find that moving the divisi back by a bar, to the start of bar 9, and then duplicating bar 9 manually to the lower staff, works acceptably well. Sorry for the inconvenience.