I have been a long time Parallels user but I just had to remove it because it has been causing issues for a while now with my macOS system and I just now narrowed it down to Parallels as the cause. My host machine is a mid-2012 13-inch Macbook Pro. Core i5 2.5Ghz, Intel HD 4000 (1.5GB shared VRAM), 16GB DDR3 RAM, 1TB SSD. Previously, it worked fine prior to Mojave. But ever since I upgraded to it, after several hours I would lose the ability to launch Messages and FaceTime apps as well as use "About This Mac" and Restart/Shut Down windows would not display. Keychain would work but it would not bring up the password prompt if I needed to view a stored password. In order to restore functionality temporarily, I needed to reboot via Terminal and then I would have access to those functions again but only for a few hours. I uninstalled Parallels and it's been 2 days now without this issue. I started with a clean slate, slowly adding back apps and things until I saw the bug return. It only happen after I installed Parallels. It took me several days to get to that point (seeing how long, if at all, various apps would trigger this issue). What about Parallels is causing this to happen? Note, this was happening without Toolbox for Mac being installed.