No Digital Audio passthrough on firestick

On a brand new firestick max I cannot get any digital audio signal passthrough with VLC player, only comes thru in 2 channel stereo. Streaming files from local network source, WiFi6 600mbps+, multiple .MKV and .MP4 files tested. Files tested work correctly with native Samsung TV app and Plex on firestick. Netflix and Prime video also work properly from firestick in 4K and digital sound.

Equipment

Firestick Fire TV Stick 4K Max streaming device, Wi-Fi 6
Samsung UN75NU6900F (optical out to receiver)
Yamaha RX-V475 (Optical in) Configuration
VLC version 3.4.3
VLC "Digital Audio output (passthrugh)" option enabled
Firestick audio "Best Available"

Additionally tested with firestick directly in receiver, no digital audio there either. Files tested are all very large. Happy to replicate issue with a smaller test file if you have one you guys use already, please send link.

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