Currently selecting root is not the recommended course of actions. Most of the files can very easily be recovered from installer packages or are completely useless for restore purposes.
For now CloudBerry Backup for Linux/Mac only features File Backup which does not guarantee that backup/restore would produce a working machine right after restore.
Instead, we recommend running backup of only specific system configurations, production data, and users' data.

We usually recommend to backup contents of:
/home (user files)
/etc (daemons configuration files)
/var/* (only the subdirectories that are needed, like /var/mail, /var/mysql, /var/www etc.)

In some cases, you might also need to backup data from:
/media or /mnt (if there's a mount point containing valuable info)
/root (if there is any important information or settings in the home directory of the root user)

And this is what should not be included in the backup:
/boot
/dev
/var/run
/tmp
/sys

Here's the standard that describes filesystem hierarchy, might be useful to identify what to backup and what not to: https://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard

So the first thing I can suggest is to update your data set, and if the problem persists please open a ticket in our support portal.