Audio Pass Through issues – only works with external player

I hate this, asking for help and bothering people but, I’ve exhausted everything I know about Kodi to try and figure out what the heck is going on here.

I have Kodi installed on a Win7x64 HTPC using HDMI out to a Sony AVR then to my TV. I have all the required “passthrough” audio options selected. However, when I play any .MKV using any audio source (DTS / DTS-HD etc) my AVR will only display “PCM” on it.

Now here is where it gets weird; if I launch that same .MKV in Windows Media Player (using Shark’s Codecs) the AVR will then switch to “DTS-HD” or whatever audio coded the .mkv is using. So, I’m assuming that the issue is with KODI itself?

I have attached screenshots of my current audio setup so you all don’t think I’m a complete idiot and my DEBUG log:

My Debug Log

Again, sorry to bother you all. But, I’m trying to ween the S.O. off of WMC and in order for her to jump on the Kodi bandwagon, I need the thing to actually work the correct way.
( I have another issue with the recordings from the DVR / WMC not showing up correctly, but that’s for another time)