For the most reliable way to back up SharePoint Online to local storage, I highly suggest utilizing the SharePoint backup tool. This comprehensive software allows users to fully back up their SharePoint environment, including document libraries, site pages, forms, templates, site assets, and style libraries.

One of the standout features is the ability to create and schedule backup jobs to run at multiple timeframes, providing flexibility and ensuring that backups are always up-to-date. The software is packed with all the necessary features to make the SharePoint backup process efficient and straightforward.

for more info: Backup SharePoint