I confirmed the issue, I assume this is a permission issue, because if you start the batch file, it runs as your user. But if the RPA software starts it, it runs with the reduced permissions of the web browser (that is where the RPA core “lives” as extension. So with a batch file it seems no file operation works, not even rename or copy.
Solution: Use a VBS script instead. Everything works there! I tested with this script:
' VBScript
Dim FSO
Set FSO = CreateObject("Scripting.FileSystemObject")
FSO.CopyFile "c:\test\ttt.txt", "c:\test\justacopy.txt"
FSO.DeleteFile "c:\test\ttt.txt"
WScript.Quit 123