@jorge code
I have been unable to recreate the error in 20000 seconds of model time. Is this the same model that has the error?
Based on your explanation, you want two people to pass from the fila lenta to the para lentos, and then you want 5 people to be attended to in the para rapidos? Does that mean you want 5 people to move from the fila lenta to the fila rapida after it process 2 people? Or do you want it to Process 5 people in the para rapidos in the same amount of time it takes to process 2 people on the fila lenta? Do you want the fila lenta to process 2 people at a time, and that's when it is throwing the exception?
The error you are getting means the unload task in your Process Flow for the fila and para rapida (the process flow block on the left) has an invalid reference. In other words, one of the fields is trying to reference something that either does not exist or that is referenced incorrectly.
If you can send me a model that recreates the exception I can help you fix it better. Feel free to tag me when you reply so I see it first. Also, I would recommend adding a sink to the end of your Process Flow so that the tokens go into the sink, instead of sitting on the release task.