Due to the additional checks implemented in the VMware VDDK 6.0 and higher, it is inadvisable to replicate any VMware Backup Proxy or Veeam Backup & Replication VM to the same vCenter managed environment as the original VM.
According to Best Practices, the best way to protect Veeam Backup & Replication is to use Configuration Backup.
It is recommended that you regularly perform configuration backup for every backup server in the backup infrastructure. Periodic configuration backups reduce the risk of data loss and minimize the administrative overhead if any problem with backup servers occurs. It is not recommended to back up the backup server configuration using backup jobs in Veeam Backup & Replication. For this reason, you must always use the configuration backup functionality to back up and restore configuration of the backup server.