Multiple streaming interfaces on USB Audio 2.0-compliant device not functional simultaneously

[Cryowatt]

I'm currently developing a new hardware device that implements the USB Audio 2.0 class. It includes two streaming interfaces for receiving audio from the host computer, and one additional interface for sending audio to the host. I can send and receive audio to the device through a pair of the in/out interfaces, but when I try to add the second out interface, it simply doesn't work. When running diagnostics on the device, I can see that Windows is sending SET_INTERFACE requests to only enable one interface at a time. Both interfaces will send audio from the host to device, but only if the other

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