Problem when backing up on nas synology ds214se, how to solve?

Question

Backup

The ESXI 5.5 hypervisor is running on the physical machine. The virtual machines include operating systems based on Windows Server.
The legacy was nas synology ds214se. First of all, I created a mirror raid and brought nas into the domain. Partitions for backups have been created.
But I ran into a few problems. When manually creating and using a bat backup file, errors appear. (With access rights on the side of the nas server, I checked everything in order more than once) I tried to specify a different folder when creating backups, that is, my workstation with a shared folder, then the backup is successful.
I also noticed that the same error appears in the logs on the server during backup.

I've already tried different methods. I even created the WindowsImageBackup folder and still no result.
Found an error in the Windows log

Answer 1

What and how exactly do you back up? How is the NAS connected, what protocol is used for backup? CIFS? FTP? SFTP?