I am having a host of problems with Parallels 12 - all of which did not occur with version 11. Here's a short list of issues: Windows programs run extremely slowly, with both slow program response and slow mouse behavior Programs do not open properly, e.g., open to a blank document, when selected from the Windows Applications folder in the dock; they do (usually) open when selected from the Start Menu Setting the default program (OS x) with which to open a file type does not work with Parallels 12, i.e., a pdf file is set in OS X to open with Adobe Acrobat Pro (Windows version) but double clicking on a pdf file does not open Acrobat Pro When a program does not open properly (as in 2 above) and it is selected again from the dock, then menu items in that program's menu bar (OS X menu bar) do not function properly, e.g., File>Open, or Adobe Acrobat>Quit Adobe Acrobat, doesn't work I am using Windows 10 under Parallels 12.1.3 on a 27" Retina 5K iMac (late 2015) running macOS Sierra 10.12.3. I generally run in coherence mode, as I did with version 11. All the problems began after 'upgrading' to Parallels 12. I believe a major Parallels fix is badly needed.