Using A Load Generator

I have a script that uses certificates for authentication. I have a parameter for this with 400 cert names. My setting for the parameter is Unique, Each Iteration and Continue with last.

When I run all 400 users on the controller, 

User 1 gets Cert 1 and uses that for each iteration
User 2 gets Cert 2 and uses that for each iteration
User 3 gets Cert 3 and uses that for each iteration

However... I have introduced a load generator to the mix. The parameter data file ins stored on that laptop in the same directory as the controller.

When I run I am having this problem.

The first time User 1 runs, the script uses Cert 1 but then uses Cert 2 for the remainder of the time of the test.

Each user does this where it uses a Cert and then increments to the next one. This is causing errors as all my Certificates are used up after 200 users so the other 200 users fail.

Any help would be appreciated.

Thanks,

Barry