Windows: Scheduler task, GPO and wbadmin command in Workstations

Hello everybody, hope everyone is Ok, first post here.

After racking my brain for three weeks trying to apply a task that executes the WBADMIN command on each workstation, I still can’t find the correct answer, so I came here to ask for help.
In Windows Server I created a GPO to run a scheduled task, the task, run the wbadmin command and thus perform backups on a NAS.

So far this is my ongoing:

The only way to deploy the task it’s thru the SYSTEM account, as administrator no way jose.
The SYSTEM account cannot run the WBADMIN command. (the task starts without problem, but not the command)
I created a batch file, with the WBADMIN command, and gave the account SYSTEM the permissions (local and domain) to run the batch files. (the task run without problem, but not the command)
I created another batch file with runas command, so it can be start the first batch file (task run without problem, the batch file with runas command ask for admin credentials) (useless)
Created a user and added it to the Backup Operators and Administrator group (local and domain) change the admin in runas batch file (it doesn’t execute command, access denied)
I have tried creating files in .ps1, .vbs and .exe with the same result, it just doesn’t do system backup.

In Windows Server I executed the command wbadmin with the psexec commad from the pstools, and everything go as it suppost to go, but it’s in Windows Server, no idea how can run psexec in every workstation.

The solution must be only based on Windows.

Am I missing something here?

Thanks in advance.