The OneDrive sync client is an important Microsoft 365 component which underpins features like autosave and coauthoring of Office documents. During the March 15 Azure AD outage, the client had a meltdown and removed all the local copies of files stored in a SharePoint Online folder, seemingly because it couldn’t authenticate. The problem was easily fixed, but it’s a bad example of handling what could be a transient authentication issue.
https://office365itpros.com/2021/03/17/onedrive-sync-client-meltdown-during-azure-ad-outage/
