DiffNote - NoteDiffFileCreationError "Failed to find diff line for <file>"

Summary

The customer is seeing the following background job failing over and over again.

13 hours ago create_note_diff_file CreateNoteDiffFileWorker
DiffNote::NoteDiffFileCreationError: Failed to find diff line for: <file_here>, old_line: , new_line: 202

13 hours ago create_note_diff_file CreateNoteDiffFileWorker
DiffNote::NoteDiffFileCreationError: Failed to find diff line for: <file_here>, old_line: 383, new_line: 527

Deleting them from the queue will remove the dead jobs but after a while, new ones are being reported again.

related ticket: https://gitlab.zendesk.com/agent/tickets/207156 (internal only)

Additional Information

The customer noticed that when a URL is called like https://$HOST/$GROUP/$PROJECT/-/merge_requests/$MERGE_REQUEST_ID/discussions/$ID, then the background job is created and the problem starts to occur. They need to manually delete the dead job from the queue. That URL is used to load the notes/discussions on the page.