OK - finally sorted it out it appears what was missing was the inverted commas around "[Device.Password]"
"C:\mikrotik\winbox64.exe" [Device.FirstAddress] [Device.UserName] "[Device.Password]"
just to throw this in here too
This works for a static always use this username/password regardless of what device is saved with and regardless what is logged into DUDE
c:\winbox.exe [Device.FirstAddress] username password
This one logs in pulling from DUDE log in
c:\winbox.exe [Device.FirstAddress] [Admin.Name] [Admin.Password]
And testing, this works fine in our DUDE
c:\winbox.exe [Device.FirstAddress] [Device.UserName] [Device.Password]
May be related to you having "" at the directory which shouldnt be needed since you have no spaces in the directories names