Same problem, been using parallels since V9. Ever since upgrading to 15 it crashes, usually every couple of days, most often on Chrome or Outlook, most recently with word. When I try to restart Parallels it freezes the Mac OS. I have to restart the mac several time and wait 5 or so minutes for windows to sort itself out. I tried downloading to v14 and its ok but does not integrate well with the new versions. If this is not fixed soon, I am going back to bootcamp and removing parallels. This has wasted far too much of my time.