Unable to Back up On-Demand Files (code 1633)

Situation

A backup plan failed with one the following error messages:

On-Demand files cannot be backed up due to known Microsoft issue. Try to fix OneDrive.

2023-05-28 08:02:08,500 [PL] [1] ERROR - An error occurred (Code: 1003) Description: The tag present in the reparse point buffer is invalid.

Cause

This error occurs due to OneDrive application-specific internal error generally related to a problem with OneDrive objects synchronization.

It could happen if the local OneDrive directory that you are trying to access for backup purposes is corrupted, or if any operating system processes prevent the OneDrive application from synchronizing its objects successfully.

Solutions

Solution A

Reset or re-sync your local OneDrive application as described in this Microsoft official help article.

Solution B

Run "chkdsk" command in the elavated (i.e. launched under local administrator account) Windows command prompt:

chkdsk C: /r /f

Where:

C: - Disk letter for a drive that is going to be checked. Specify the letter of a disk that contains your OneDrive-related directories (in most cases, it would be a system volume "C:").
/f - Parameter enabling the disk error check.
/r - Parameter enabling the recovery of a readable data from faulty disk sectors.

Solution C

Exclude the affected OneDrive on-demand files / directories from the source scope of your backup plan.