Don ... before you do ANYTHING do a 'FULL RESOURCE BACKUP' and save it on a USB ...
I obviously made some error when I did the latest Pa900 upgrade, because a lot of things got switched around ... Song titles in my custom playlists were looking in the right place for the associated style, but the style was no longer there ... Sometimes KORG might add a new style or two and change the locations of the styles ... If you want to upgrade and don't care if any new styles are going to be added, do the OS upgrade WITHOUT the resources ...
Doing the Factory Restore for 1.20 might have some new styles, and potentially cause a 'location' problem
Whatever you do, you would have your current settings to go back to if necessary ...
Hope this helps ...