Permission issues after restoring system from tar.gz backup

[lockheed]

I had a btrfs root partition issue on my server and I restored it from tar.gz backup with
$this->bbcode_second_pass_code('', ' tar -zxvpf /fullbackup.tar.gz ')

However, now I seem to have some strange issues. For example, when I try to access user's crontab, I get:
$this->bbcode_second_pass_code('', 'You (malina) are not allowed to access to (crontab) because of pam configuration.
')
In fact, I even get this issue when I try to switch to superuser:
$this->bbcode_second_pass_code('', '$ su
Password:
su: Authentication failure')

What might be causing that and is there a way to fix it?