I have similar dramas but most notably on single clicks. When I click the little “e” on inserts, often Cubase thinks I want to drag the insert around. I honestly think this problem may have started in Sierra but I’m not sure. I seem to have the same problem in Cubase 8.5 within Sierra.
Are you folks having similar issue to this with a single click as well? Happy to provide a vid to better explain it if the problem is not clear.
I’ll likely roll back to El Capitan at some point to see if that fixes it.
It honestly is driving me nuts too.