Solution
While operating in the parallel or batch model, use synchronization steps, such as lock steps, to prevent code from calling the instrument handles in more than one instance. Create code modules after the instrument modules to process the data for results and free the instruments to take the next measurement.
The number of threads that can be executed when testing from hardware will always be equal to the number of Devices Under Test (DUTs) / The number of simultaneous channels available on the hardware.