The Jerky and slow zoom function while in a locked viewport in paper space has been a problem for many years apparently. This issue came up after an autocad reset I did. I have explored this issue on the Autodesk Knowledge Network forums but no one seems to have an answer.

To duplicate the issue, go to paperspace, click inside a locked viewport to go to the model space, then without selecting anything in the viewport, try zooming. It jerks with a delay like in steps. It is not a smooth zoom, like it is outside the viewport. And if you zoom in or out by a large factor, it can take a minute to catch up.
Very annoying, and this did not happen before I reset my Civil 3D program.

Has anyone on this forum found an answer?

TT