What exactly is device Q:? Network share, USB disk, local disk? It am wondering if it is that disk that is causing your weird issues (working, not working).
Q:\ is a network drive that all Quality Documents are stored on, including CMM programs.
You can also receive errors if the typed in value violates the naming schema for windows folders and files.
Also remember that variables/inputs update upon execution for this script.
aka, have to run variables and inputs, then the script during execution.
I don't think the script will pull the variable value if you just push play.
Just trying to throw out some ideas for error checking.
