it is not a question of money but the pleasure to do it is even and to evolve.

I am attaching a diagram of the mysensor part of my installation.
At the moment, I have the cellar's ethernet gateway working.
The usb gateway also works but only towards the 4relais card which controls my 3D printer, The card which controls the mechanical ventilation of the ground floor no longer works.
If I remove the cellar gateway The card that controls the mechanical ventilation of the ground floor works again.
Daniel

I think that now it works

have followed your advice the two gateways are working properly together. I leave several days in the test to see if it holds up over time.
I thank you for your help because alone I could not find the solution.