This happens a lot more now than it used, but it has somewhat been there for a few versions now.
I have a score and I double click in a staff to add music. Dorico moves the view and the caret to some unrelated instrument. This has occurred in some cases (not all) as many as 6 to 7 times before the double click works for the staff I want. Here is an example of it happening where the 3rd time is what works.
Robby
https://drive.google.com/file/d/1SFDQa0XNVcVO9dpRqrTgyAxCtHJLG9Kz/view?usp=sharing
Dear Robby,
I know this is not the expected answer, but it is my understanding since Dorico 2 or smth that the proper way to start note entry is shift-n or Enter after selecting an item. But, like you, I still have the habit to double click 
If this is reproducible, Robby, please attach the project and details of where the problem occurs.
I certainty will. I want to say it is not reproducible, as sometimes it takes 6 double clicks to work, sometimes it works right away. It isn’t for every project, every time. It seems if the project is open for more than an hour, I start seeing it happen on a more frequent basis.
I’ll do my best to pay more attention to the details to try to pin it down.
Robby