Just to report similar issues on my setup. So far if I start a project in Cubase 8.5 I am not seeing issues with automation with VCA or group tracks (only small projects tested) . When I open up an large project in Cubase 8.05 that was completed in Cubase 8 I have audio dropouts due to automation issues. The same project plays fine in Cubase 8.03.
I am on Windows 7 Ultimate 64bit Service Pak 1 , hex core 3930K with dual RME raydat cards