I just did a fresh installation of 1.2.0 RC10 on a Zotac nano. Installation used all default options, and no error messages seen.
I then rebooted the box, changed the config (changed IP addresses on Ethernet interfaces), did a commit and save (all with no error messages). I rebooted again, but all of my configuration changes were gone (Note: the password set for user vyos, during the installation was saved).
Multiple attempts and multiple reboots - all the same.
I then did a fresh install of 1.2.0 RC8. Again - same default options, no error messages.
Saving the config works fine!