I'm design a autopilot rudder control system for a ship, so I already design four controller (PID, lag/lead Compensator and Lag-Lead compensator) and it worked.The problem I have, it happen when I design the perturbation. The perturbation is a second order transfer function and its input is random number to 0-50, so I put de block random number block and multiply by 50. When I run the simulation, the simulation goes very slow and stop 20 seconds later. Consequently, I quit the random number block and I put a control block where I can change the value manually and the simulation run very well. 

I think the problem are the time when it happen the changes with the random number block but I don't know how to fix it