Windows update 1803 messing with sound output

Ever since my Win10 Pro updated to v1803, the multichannel sound output has been wonky, or flat out missing.

In most cases it's not a huge deal, since for youtube videos and most games where I don't need positional audio I keep it on All Channel Stereo (meaning it sends the same signal at the same volume across all speakers according to settings), and for CSGO I use multichannel setting with 5.1 in the CSGO sound settings. Now my receiver will default to All Channel Stereo if it doesn't receive a valid Multichannel signal, which is fine.

What is not fine, however, is the fact that some sound channels appear to be missing - when this issue occurs. Most notably the centre channel. If I play a 5.1 video file in VLC, basically any audio except for the main dialogue will play, regardless of the audio output setting in VLC. Youtube is mostly okay since it's stereo - but I've encountered several videos both new and old where I only get sound from a single channel, often the left one.

CSGO is a different beast, as even with All Channel Stereo supposedly being output from my receiver, some sounds are missing, as Windows apparently refuses to send those channels through. So I'm stuck with playing a game with half the sound actually playing.

On my system it sends sound through HDMI on my 1070 GTX to my Onkyo TX NR-3009 receiver where it passes the image through to my tv (and separate DVI cable to a monitor).

I've tried updating everything, rolling back some nvidia drivers but to no avail.

Used SPDIF from the motherboard to the receiver for a couple days and didn't have this issue, and that would be natural since it isn't capable of multichannel.

Many people are having various issues with their sound on various sources/output methods after updating to v1803.

I have found a "workaround" to reset this. Either turn off the digital audio and re-enable it in the Nvidia Control Panel, or swap to whatever else and back to 7.1 in the sound options in the taskbar. I would prefer a more permanent solution.

Any ideas, or are we basically just waiting for Microsoft to fix whatever it was that they fucked up?