mysqlbackup ERROR: Backup directory already exists and is not empty (no replies)

Hi,

I'm testing MEB 3.6.1 and getting the following error when using mysqlbackup with --force option:
mysqlbackup ERROR: Backup directory already exists and is not empty

Here are the options in /etc/my.cnf file
[mysqlbackup]
user="dba"
password="password0"
force="TRUE"
databases="test_db"
backup-dir="dbbackup"

I execute the mysqlbackup command as follows:

./mysqlbackup backup

Any advise is much appreciated!

Thanks!
Joanne