Field server backups contain a checksum used to validate the backup when restoring. The validation is done to avoid that the backup has been tampered with.
When you restore a backup, the checksum is validated. You are notified if the validation fails by an error message. If you suspect that someone has tampered with the backup, you can abort the restore. If you are sure that no one has tampered with the backup, you can procced with the restore process.
Replacing a faulty field server with new hardware always result in checksum error. In this case it is acceptable to proceed with restore if there are no indications or suspicions that the backup has been tampered with.