Forum rules: Just please remember to play nicely once you walk through the door. You can disagree with us, or any other commenters in this forum, but respect our space and keep your comments directed to the topic at hand.
I don't use the backup option - I have a cron job that backs stuff up to offsite. However - this will be running as the web user (usually www-data) so make sure it has r/w access to whatever directory you're trying to write to.
Report your issues and feature requests; https://github.com/opencats/opencats/issues