ssh persistent error "Permission denied (publickey)."

One fine day while checking up on cron backup job on the server, it recorded an error while doing a rsync to the backup storage server. All other users have no problem login onto the backup storage server, just this particular username have problem. After checking out the interactive verbose output of the attempt ssh server session, public & private key, log files, server user's credentianls, below is the solution :


Problem :
ssh to server that uses only public key authentication only persistently got,

Permission denied (publickey).

Checked log file and got,

sshd: Authentication refused: bad ownership or modes for directory 
/user/home/directory

Solution :
Change to a more restricted permission of the home user directory.
e.g.

chmod 750 /user/home/directory

Voila !!!