I'm having very similar multi_switch errors. But in Designer it compiles and exports the sbsar normally. The errors only occur when trying to open the sbs file on Substance Player. Opening the sbsar on Player is also normal. I guess it has to do with some incompatibility between the 6.0.0 Player Linker and the 6.0.2 Designer file.
I've attached my substance file. The node giving the errors is the one connected to the BaseColor output. It has a function to select the correct input and the only possible outputs on that function are either 1, 2 or 3. So I don't understand why it gives me errors asking for inputs from 4 to 20.
But, as I sad, it only gives errors trying to open the sbs file on Player, cause it then compiles the file by itself. Exporting an sbsar from Designer and then opening it on Player is fine.