Cron backup error while creating Backups

Error messages:

tar: ./nd/00/00/00/00/00/03/CA: File removed before we read it 
tar: ./nd/00/00/00/00/00/03/CB: File removed before we read it

This can happen if changes are being detected while the backup is running. The tar process will be the backup task, the error is due to a file being removed while the backup was running.

Please confirm that the backup is running during a quite time and if these backups are completing as scheduled.