Microsoft Teams backup fails with the "Object reference ...
https://www.veeam.com/kb420125.08.2021 · Error: Object reference not set to an instance of an object. Cause This issue is related to recent changes in Microsoft Graph API response syntax to a specific request that Veeam Backup for Microsoft Office 365 uses to process Microsoft Teams. Solution This issue is resolved by Veeam Backup for Microsoft Office 365 5c cumulative patch KB4187