I got problem with the sound. I need to open the project twice to get the sound. but the worst of all is that the bottom of my mixer I gone. I cant drag it left or right to get to tracks anymore. the option is gone. and the master bus is only half… I can only see the left side of it and that takes away the option to open the edit window on the masterbus. both on full screen and on scale .I did the upgrading two times but it didn’t solve anything. I tried the zoom palette but no help . I think is very strange that steiny put out such a bad virus on their own software. and when they finally come with a upgrade that is suppose to fix things : always on top - on the mixer is not with it ! can you believe it ? you still have to continue to press f3 some thousand times. this is really bad steiny. what are you up to ? yeah ok it could be my pc, but I don’t think so. c7 work fine, also c7.5. I`ve been with Cubase for 5 years now .all the problem stared on c8. I think somebody in steiny are too smart for their own good. screwing up things for the rest of us. still faithful ,but for how long I wonder ? the support used to be good, but now its not !! 
Close cubase
Delete all files in your preferences folder. C/users/you*/roaming/steinberg/cubase 8_64
(Delete everything in that folder - might wanna keep your key commands)
Restart cubase.
Set everything up.
Close cubase.
Backup your new working preferences folder.
I had a lot of problems when I went from c7 over to c8 and I did that many times after advice from the support, but when it solved one problem it created a new one.in order to fix the new one I had to do it again and again…until I gave up .thanks for you kindness but I am not going to do that. c8 is a problem child. lets hope steiny very soon comes with c9 hopefully without problems. I understand that they can make mistakes, but this upgrade is no good.
Ok…
Make a coffee, go for a run, roll a joint or do whatever you do to get your mind at ease.
Let all your stress go and take a timeout from your worries.
Pop on some nice background music and do the steps above…
It will take you 5 minutes to set everything back up… → whats 5 minutes in the grand scheme of things, eh?
Come back to this thread if it didnt work or if you need any further help (or pm)
Oh, and update your gfx drivers
when I went from c7 to c8 I had problem and the support told me to do the same thing that you do. when I downloaded the New grapic card the Whole pc crashed,it took me days to get it right again. I did get it right With a New updated grapic card . it did solved the problems I had then. thanks again for all the good advices but until there is a very sure upgrad or something like it…I am just gonna live With it. but am not happy With steiny. it’s like they dont care ,Yeah thinking about it am gonna post helge vogt a mail…he’s gonna get it !
but truly thanks again.
New day, new luck, new possibilities;)
Give us some detailed specs about ur machine n software so we can help…?
P.s. Helge is a good cat… -surely he is doing what he can;)
I had something similar to this. I had no scroll bar in the mixer.
What I did was run a system restore from before I installed 8.0.20, and then after that reinstalled 8,0,20 update and that cured the problem.
I’m not at my computer at the moment, but there is a mixer reset feature. Wouldn’t this fix your problem? There is a drop down list you can get to by clicking on something in the upper right side of the mixer… If you click it while holding one of the modifier keys (ctrl or shift, etc.) a mixer reset option shows up. This fixes a weird mixer sizing issue I used to have where the mixer suddenly would be larger than my monitor screen size and the bottom part was cut off such that I couldn’t see the horizontal scroll bar or track names or even the mixer volume sliders for tracks set at low gain.
I finally get the best solution after taking the advice and use the restore setting to an earlier time. I went back a week and got back 8.0.10 and the mixer is back. 8-0-20 is crap ! am not gonna jump on the next upgrades from steiny so soon. that was a mistake
I had a similar thing - side chaining wouldn’t work at all in 8.0.20. i reinstalled 8.0.10 and all back to normal. although i had to time machine my key commands!
For the time needed for the project to open?
I went from about a 45 second opening to about a 25 minute opening.