Unable to upgrade from 10.3-RELEASE to 11.0-RELEASE

[dabo]

Hi,

I’m trying to upgrade my FreeBSD server from 10.3-RELEASE to 11.0-RELEASE with freebsd-update -r 11.0-RELEASE upgrade, but it doesn’t work. 
It fetches 45588 patches and in the end it cannot apply them.
####
Applying patches... /usr/sbin/freebsd-update: cannot open patchlist: No such file or directory
done.
/usr/sbin/freebsd-update: cannot open files.wanted: No such file or directory
rm: files.wanted: No such file or directory
rm: filelist: No such file or directory
rm: patchlist: No such file or directory
####
I already removed all files from /var/db/freebsd-update but without success.
Has anyone an idea?
Is it possible to upgrade by CD/ISO without replacing changed files in /etc?

Many thanks
dabo