Where do you see the message “Configuration Error - Database dump failed.”?
I don’t think starting over is necessary - we just need to understand what the situation is so we can tell you how to fix it.
You can run a manual database dump at any time.
Use that to get a shell inside the cms-web container. Instead of running mysql -u cms -h mysql -p cms to access MySQL command line, you instead run:
mysqldump -u cms -h mysql -p cms > /var/www/cms/library/temp/backup.sql
That will create a file backup.sql in your CMS library temp directory, which you can pickup from outside the container.
Assuming that works, then I would guess that the password you’ve chosen for your MySQL user contains special characters (ie isn’t long and alpha-numeric only), in which case the special characters can prevent the backup working properly.
You’d need to change it to something that fits the requirement in your config.env file, as well as inside MySQL itself and then down/up the containers. Automatic backups will then work as expected.