OneDrive error “The tag present in the reparse point buffer is invalid”
This warning may appear if you are using the OneDrive Files On-demand feature. If you have chosen to backup the contents of your OneDrive folder, the backup client may be trying to backup placeholder junction files/folder kept by the On-demand feature.
The message: "The tag present in the reparse point buffer is invalid"
Indicates that some of those junction files are likely in a damaged state, this could happen if OneDrive had crashed or terminated improperly at some point.
Usually this can be fixed by running chkdsk.exe from an elevated command prompt by running 'chkdsk c: /f'.
Be aware that running this repair may require a system reboot.
You may also want to see this article to disable the OneDrive Files On-demand feature so that you can backup files stored on OneDrive.