More than one input connectors on a mechanical equipment

[adcdao]

Hi, I created a mechanical equipement family for exhaust air with filters. I add one connector for the input and one for the output. Everything is working well. Now I want to add a second input. The flow is correctly calculated and I sum the 2 inputs for the output. But I lose the possibility to calculate the drop pressure. With one input it's ok but with 2 inputs I have this warning:

Any one can help?

Thanks,

André