I used fit data task and then tried to simulate the estimated parameters with simulate data task. The outputs are different. I played with different simulation setting options and found out that OutputTimes option changes my output (significantly). I also created a separate ode function file and simulate the same model; output of this file matched fit data task's output. Long story short, I cannot duplicate the results from fit data task with simulate data task in Simbiology. Any suggestion would be appreciated.