simulation – Error of ModelStructure/Outputs by using FMU container

I am trying to combine three FMUs into one FMU that contains all of the three. Specifically, I have one FMU of a pandapower electricity network and 2 FMUs that are CSV files converted to FMUs by using PythonFMU tool. All of the FMUs have been tested by the FMU Check and they have been simulated together to check that everything works fine.

Then I am using FMPy tool to combine all of them together and export successfully the final FMU.

However, when I am trying to validate this I get the following error:

ModelStructure/Outputs must have exactly one entry for each variable with causality="output".

Any idea of what is wrong here?