The SMBus most likely is the culprit and has a driver assigned, preventing you from passing through the audio controller (both in the IOMMU group 9).
To get around this, you'll need to prevent Unraid from assigning the SMBus driver upon boot by adding "modprobe.blacklist=i2c_i801,i2c_smbus" to your Syslinux configuration append line.
Just navigate to this page:
https://cronos/Main/Flash?name=flash
And modify the green block's append line:
Then hit Apply and reboot the Unraid server. Your Windows VM should be able to start after that.