I just saw similar thread and wanted to ask this without hijacking the other.
I use Maxwell, and it uses the Rhino camera (including focal point) for defining the render. I create a new viewport and camera, toggle it visible and then use the camera points to line it up perfectly. I then set the focal point for the camera specifically where I want it.
As soon as I click in another window and go back to my render window, it changes the focal point. Every time.
It would be great if you could just lock a camera so it couldn’t move at all. There have been plenty of times I accidently bump my space mouse and move my camera off of it’s location.