Problem with EPANET model simulation

There is a big problem when I want to run many timesteps in a model. No matter what demand multipliers I set in the model at each timestep (each multiplier at each timestep has been successfully put in the model), starting at 36th or 37th timestep, EPANET model just returned the same set of simulated pressures.
I have no clues about why at first several timesteps different estimates could lead to different set of simulated pressures but resulted in the same set of simulated pressures starting from 36th or 37th timestep.
The model can be downloaded in the web link: