I have red about this bug before, the last time was in patch 8.02 and now with patch 8.03 still it insists.
Before i analyse the way the bug works i would like to point out that this bug occured after a format, clean install of win10 64 bit and cubase 64bit in patch 8.03, and never got this bug before (only difference was i had win7 64bit).
I first encountered this while i opened a template (custom made) with several group and fx tracks only. I quit, restared cubase, restarted windows opened another template (custom made) and still the scroll bar in the mixer window was missing.
I use two monitors but the results are the same in both of them. I opened other projects of mine and the scroll bar was working properly. Also i tried to make a new project, added lots of audio tracks and still it was working properly, so therefore i tried to mess around with the templates that the bug was insisting.
So i re-opened my first template with about 18 group and fx channels, and added lots of audio tracks. A scroll bar appeared but it didn’t work properly, the scrolling action felt innacurate, and above all while some kind of (buggy) animation was taking place the view of the tracks was stationary (almost frozen).
Then i deleted all of my group tracks and tried the same, result was the same.
Finally i deleted all the fx channels and the mixer left with just the audio tracks and the scroll bar to work properly this time. I quickly re-added lots of group tracks and the scroll bar was still working properly.
I don’t know if someone has encountered this in his project with audio and everything, but this needs to be fixed.
Please let me know if you have more on this bug.