Error in user-defined matlab function

I am using COMSOL matlab function, and I defined two functions: full_expression_PL(T,z), full_expression_PL_dT(T,z), where full_expression_PL_dT is the derivative respect to T of full_expression_PL. I clicked the Plot, the two functions can be showed successfully. However, when I compute the model, here comes an error:

Error in user-defined function.
- Function: dfull_expression_PL_dT
Failed to evaluate expression.
- Expression: d(d((2*test(mod1.Te)*mod1.Irzt*full_expression_PL(mod1.Te,z)*pi*r)*(dvol),{test@0}),mod1.Te)

The attached file is the Screenshot of the matlab function definition window.

Is there anything wrong in the definition? Does anyone know why this happens?

Thanks!