I have a similar problem. Since upgrading to Version 13, it has been a nightmare - sometimes taking me a couple of hours of restarting my Mac, force quits, forced power-offs etc. to get Windows 10 to start. I am seriously thinking of uninstalling Parallels altogether and running Windows on a PC instead! I know that if I install an update to Parallels then I am going to have this problem. Note that I have been working in IT for more than 30 years, so I know that I am not doing everything wrong.
Just managed to get Windows 10 running - it only took about 3 hours to do that. So far this month I have probably spend about 10 hours getting Windows to start under Parallels 13.
Last edited: Oct 10, 2017