Not really a solution, but the advice we've always has is to not copy settings across major versions. Plenty of opportunities for registry key changes to mess up something on the new install and cause all sorts of instability issues.
No problems here. Also have never had any problems carrying settings across to to new major versions.
I have resolved this problem.
I had the option to load my settings as a 2014 or 2015 version. I first tried it as the 2015 version, which failed. I then tried to restore my settings as the 2014 version, which again failed. So I then tried one final time to use the 2015 version, and was successful.
I have done this across new major versions for over 5 years, with no problems. It makes my life so much easier as I have all of my custom toolbars, templates, file locations, etc. there.
Thanks for the feedback.
With each new release, I prefer to redo all the option settings anew. That forces me to go through every option page and discover all the new hidden gems.
I do load the previous versions toolbars & keyboard shortcuts though.
For what it's worth, I had big problems jumping major versions. I took the advice of redoing settings from scratch when we upgraded from 2011 to 2014, but some users restored their backed-up 2011 settings, and loading those 2011 settings in 2014 caused major instability.