Failure during install of SQL Server 2016 sp2
I've seen this error on other versions of SQL Server on a legacy build.

In my case, it was caused by the owner of a role or schema was not the default: 
Something like db_datareader was authorised by a user account (they no longer have sysadmin)

How to recover?


Could not restore master because the master database version was lower than the binaries version
Created a new install with the correct version to get it running, then restored master to that, then copied master mdf back to the original install.


Unfortunately, I can't remember the exact details now.
It's the only time in 20 years of SQL Server I've...


seen a service pack install fail that stops SQL Server running
had to deal with a version mismatch on restore of master