Different results from Matlab and Simulink from a same Iteration process

Hi eveyone,

I'm trying to solve a PDE in Simulink which is already done by me in MATLAB code through the double-iteration for two unknowns in this PDE. The problem is that i'm facing two problems by Simulink although i use the exact same process in a MATLAB-fcn block placed in a enabled subsystem block (in order to cut the process as soon as the iteration goal is achieved). The problems are followings:

1. for the first parameter the model in simulink results a quite different value. By the iteration in pure Matlab code the answer is somehow between -1 and 1 (negativ values included which are correct) but in Simulink results the iteration leads to only positive result between 0 and 2.
2. the iteration for second parameter fails by simulink and there is no convergence.

Here should be remind that the aimed result is in Matrix-form. I would be glad if some one can tell me what is the problem and why i am recieving different results from this two processes?

thanks.