Split your migration into smaller chunks and migrate them one by one. Always run only one task at a time as to not encounter the same error. (OneDrive, Teams, and SharePoint all fall under the SharePoint throttling policy so these should not be run at the same time).
The On Demand Migration tool tries to utilize as many concurrent connections as MS allows.
And we have this community post regarding this error and throttling:
https://www.quest.com/community/blogs/b/microsoft-platform-management/posts/impact-of-sharepoint-online-throttling-on-migrations
