can you post the contents of your NSH script and let us know if it is a "type 1" or "type 2"
This is how i normaly call an nexec in a nsh scrpit.
I find enclosing the command in Back Qoutes and setting a variable helps when passing multiple args to nexec from a nsh script.
Vendor=`nexec -i $HOST wmic bios get serialnumber`
As csdale said try the variable route... I usually set command output to a variable so I can run a test against the result to ensure it was successful/not.
result=$(nexec $HOST command args)
Also since it is Windows you can try the below which will execute the command from a windows command prompt and close the window once its executed (note: you will not see the command prompt window, its just a flag that tells the OS to execute the command and close the prompt)
result=$(nexec $host cmd /c net stop service)