Cubase stuck with instrument open (in background?)


I recently upgraded to Cubase 8.5 and am having a problem since that. I’m using 2 screens for cubase having the mixer and piano roll on the right screen and the main layout on the left screen.

When I open for example Omnisphere (it can be any vst btw) and I don’t click on the X in the top right corner to close it, but instead I open for example the piano roll, Omnisphere moves to the background I think. At that moment I cannot click anywhere within cubase, like it’s frozen.

In the bar at the bottom I can right click on the project, select close and it asks me to save the project or not.

In a way it’s not frozen, but something is in the background preventing me to do anything within cubase.

Does anyone have this problem? If so, how to fix it?

Also; a lot of times when I save my project I cannot close cubase itself (looks frozen) so at that moment I have to go to the taskbar and force it to close.