After upgrade you see some Skipped Changes records with Disposition 'Skipped Error' and unable to compare the record to the OOB record to review.
Skipped Errors are usually thrown for records that were attempted to be loaded but skipped, due to the record already existing in the system in a different scope. Usually, this means the record is already in the system brought in by another plugin.
There is no action needed to be taken on these records. You can safely ignore these records and set the status on these records as Reviewed.