I am having the same issues. I have a 30 mb file that runs fine when I save it down to VW2017, but in VW2018 it is a nightmare to navigate! Zooming in and out of a simple elevation takes about 3 seconds or any time I zoom or pan. Drawing a single new line anywhere in model space and VW2018 redraws every single line on the screen taking another several seconds and wasting processor power on redrawing, which is very inefficient. Zooming in and out, drawing one line, going back to sheet view, should not take an entire minute! Drafting is like pulling teeth in 2018. My service pack is up to date. Please fix! I will save down and use VW2017 until the program is made usable.