"The command which you have mentioned specifies that parameter values as Mandatory. The Exception that you have mentioned occurs if any of the attributes passed as variables do not have values populated while creating Users. A null value passed will result in Exceptions."
I've demonstrated to your support technicians that based on whether or not the fields that would pass variables are on the same page that the %variables% pass through without error, but if they are separate tabs, and those tabs are not loaded, they tend to not pass the variables through to the script.
And I have also 100% verified with absolute certainty that there is no Mandatory attribute assigned to the Param() function which receives the %variables%
Additionally all the variables I am passing through to the argument are filled. I wouldn't waste my time or your support teams time with out insuring that the most basic element to the equation is satisfied.