I know some people have reported crashes related to percussion kits. I’m afraid I’ll have to join them. Dorico crashed every time I tried to add instruments to a percussion kit in one of my recent projects.
I managed to solve the issue by creating a new kit with all the instruments I needed, copying the music and deleting the old player. I saved the old file with a different name so I’m posting this just in case someone in the team wants to have a look at it for mere curiosity.