S-function: propagation error.

I've got a problem with S-function builder in simulink. I realized a complicated S-function, in input there are matrix with cond number very high. The results are wrong if the output is feed back for using at the next step. The error increase step by step, it starts at 10^-13 and it goes at 10^3.

How it's possible that? there are any propagation error?

[Kaustubha Govind]

Do you use a Delay block in the feedback loop? This might be important if your S-function is a direct feedthrough block.