Using Mathematica, I'm multiplying two transfer functions using SystemsModelSeriesConnect. Despite yielding a result that seems correct, the operation produces the following error:

TransferFunctionModel::npnd: Unable to automatically separate polynomial numerators and denominators. Try simplifying the object.

The notebook with the code is attached.

As can be seen from the notebook, one of the transfer function matrices is very simple. The other, however, is more complicated. It was generated from a Modelica model, doing linerarization keeping a few parameters in symbolic form. Before calculating the transfer function from the state-space equations, such parameters, that were supposed to be real originally, were replaced by complex numbers.

I suspect that Mathematica expects the the polynomial coefficients in the numerator and denominator to be real numbers, and generates an error when this does not happen.

Confusingly, as shown at the bottom of the notebook, it does carry out the multiplication properly. The ratios of the elements involved yield the expected values of s^2.

Why does the function SystemsModelSeriesConnect produce this error?

It there a way to use the function without it considering there's an error?

Thank you very much in advance.

Cheers,

Fabián