Hello, I am using High Sierra as guest OS (latest version) with Parallels also in the latest version, Parallels Tools are installed. The build in screensaver of MacOS is not working. In the attachment you see the result as a "broken" screensaver preview. When the screensaver starts the screen gets dark or also damaged like in the preview. In addition sometimes the preferences app gets killed. So I think this is a major problem of Parallels. Could anybody please help? Thanks a lot! Frank.