Basically what the title says: there's no sound at all during the first ~5 seconds of the faction intros/cutscenes. For instance for the Wild Walkers video, there's no sound at all for the first two sentences ("It is coming. I am convinced.") but then it picks up in the middle of the next sentence and continues normally. I've had that with Mykara, Cultists and Kapaku as well so it's not just one faction. I didn't have this issue when playing Inferno last August, so it seems to be related to the latest version somehow.
I've seen recent Let's Play videos on the Symbiosis version and they didn't have that problem though, so it must come from my end. Before re-installing from scratch for something admittedly pretty minor I'd rather check if someone knows what could be causing this.

This issue is present whether I use the Community Patch or not. Also if I watch the movie directly from the game folder with VLC there's no sound issue at all. I already tried verifying game files with Steam (including by manally deleting one of these movies so it would be re-downloaded) but it didn't do anything.

Update: I tried a full reinstall (including removing the files from the My Documents folder that contain your last used options and stuff) and it didn't change anything. The game introduction/trailer works perfectly fine however.

And it gets weirder: while testing some changes to see if I could find the origin of this confusing issue, I discovered that if I leave a game and then quickly go to the new game menu and start a new one in about two seconds or less, then I get the full audio from the faction cutscene. It's like there's a forced silence after the main theme but if you start the game super quickly, then the main theme counts as not having started or something like that. Tried to lower the "silence between tracks" options after that but nope. Also this may just be a huge coincidence because disabling all sounds including menu music does not fix the issue either, and I know it sounds a bit like voodoo magic when explained like that but it's the best I've got.

So anyway I kinda doubt that anyone really has the time to delve on such a weird issue especially if noone else experiences it, but if anyone has any idea don't hesitate to share it.