siteXX.tgz with /home/user/.ssh/authorized_keys results in empty file

Scratching my head here. I have a site61.tgz file that successfully gets
selected during install and creates a bunch of directories and files
(including /root/.ssh/authorized_keys), but for some reason
/home/user/.ssh/authorized_keys ends up empty.

After install and before reboot:

# cd /mnt
# ls -la home/user | grep ssh
drwx------ 2 1000 1000 .ssh

# ls -la home/user/.ssh | grep auth
-rw------- 1 1000 1000 authorized_keys

which are the correct permissions. Now, if I do:

# cat root/.ssh/authorized_keys > home/user/.ssh/authorized_keys

everything is okay.

What is going on? Why is the process extracting siteXX.tgz
treating /mnt/home/user/.ssh different than /mnt/root/.ssh?

*continues scratching head*

Cheers.
Erling.