SQL Backup Error 3266

My backup are failing daily with these error message:

The backup data in ‘TRates_BackupToDEV’ is incorrectly formatted. Backups cannot be appended, but existing backup sets may still be usable. [SQLSTATE 42000] (Error 3266) BACKUP DATABASE is terminating abnormally. [SQLSTATE 42000] (Error 3013). The step failed.