Dear Khaled, I have not try model1 so i can not comment on it. When I ran model3 after the modification that I mention before. MG refuses to make the computation for the process that you mention because it can not handle it. This is process specific, so it is possible that you test for another process, I do not know but if they are indeed the same model then I would expect both to fail. Cheers, Olivier On 27 Jun 2015, at 15:02, Khaled Teilab