I’m experiencing the exact same problem except with two Sonos “One”s, a Sub and a Beam. With a NUC too (7i5BNC)

It looks like a known problem with Windows.

If you find a solution, be it a hardware one, please let me know.

Cheers

Is the problem because you are playing media with DTS encoding?

Beam will only accept Dolby Digital.

In Kodi’s files view If you select the media (without playing it) Kodi should show how it is encoded.

You can get Kodi to translate DTS to Dolby Digital. Go to Settings->System->Audio.

Set “Number of channels” to 2.0 (apparently this is a setting for PCM and should be set to this when not using PCM)

Scroll down and set

Allow passthrough: true
Dolby Digital (AC3) capable receiver: true

-- Enable Dolby Digital (AC3) transcoding

DTS capable receiver: false

A warning: the translation will introduce an audio delay. This can be counteracted by changing the audio offset. You can make this the default setting so that everything played has that offset.

The only trouble with that is if you play Dolby Digital it will get delayed unnecessary so the audio will be out of sync again. This is annoying and ideally Kodi would allow you to set a delay for DTS only.

I've the same problem with a Beam and two Ones. My NUC is a little older, and LG TV. Whe I try to configure the surround speakers, I can only see stereo option...