Mr Ozzy those modules are not necessary and supported in LibreELEC. Those are only available with Hardkernel's Kernel. We use a more recent AML Kernel but it lacks individual fixes from HK. Hifi Shield should just work with simultaneous HDMI audio output.
TheCosmicSlug was is tested with my new leia24 release?
Yes tested with the leia24, ive been having issues ever since leia21 but it seems to have finally gone 
If it helps anyone still experiencing them, try this:
In Kodi settings > Player > Videos then set:
- Adjust display refresh rate > Start/Stop
Sync Playback to display > Off