How to mix gases with different properties in Simulink ?

Hello everyone,
I work on a project where I have to use three different gases for mix them :

I use simulink for obtain the density of the gas mixed but I have this error message :
"Error compiling Simscape network for model labo.
Caused by: [‘labo/Gas Properties (G)1’, ‘labo/Gas Properties (G)’]: Failed to propagate domain parameters. Domain parameters are propagated to the same set of nodes from sources: ‘Subsystem10.Gas_Properties_G1.A’ and ‘Subsystem10.Gas_Properties_G.A’. Each node may only have at most one source of propagation."
So, how can I mix different gases if I can’t define a physical constant for each of them ?
As a reminder, I don’t know gas properties for the mixed gas.
Thanks for your helpHello everyone,
I work on a project where I have to use three different gases for mix them :

I use simulink for obtain the density of the gas mixed but I have this error message :
"Error compiling Simscape network for model labo.
Caused by: [‘labo/Gas Properties (G)1’, ‘labo/Gas Properties (G)’]: Failed to propagate domain parameters. Domain parameters are propagated to the same set of nodes from sources: ‘Subsystem10.Gas_Properties_G1.A’ and ‘Subsystem10.Gas_Properties_G.A’. Each node may only have at most one source of propagation."
So, how can I mix different gases if I can’t define a physical constant for each of them ?
As a reminder, I don’t know gas properties for the mixed gas.
Thanks for your help Hello everyone,
I work on a project where I have to use three different gases for mix them :

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