What does this sync error mean?

[warrenc59106081]

• ▪  error:
  • message: Upload rejected
  • permanent: false
  • resultCode: 1005
  • resultData:
    • code: 1005
    • description: Input Validation Error
    • errors:
      • parent_revision_id:
        • 1: must be the head revision
    • subtype: InputValidationError
  • time: 2018-02-08T17:14:44.756Z
• timestamp: 2018-02-08T17:14:41.635765Z

This is a sample of the sync errors for a large migration to Lightroom CC. About 6% of my files show this error.

What dose it really mean and more to the point how can I fix iT?

[selondon · Accepted solution]

You may have some luck posting here, as Adobe engineers have a better chance of seeing it:

Lightroom CC | Photoshop Family Customer Community