XML profile files on plex media server

Can someone explain exactly how the XML device profiles are handled by Plex and what if anything overrides them?

I have a plex media server setup on my network. I use an android device with the plex app to cast media to the chromecast plugged into my TV. It seems to work with pretty much everything except files containing AAC5.1 audio. Instead of transcoding them it tries to play them and fails because the chromecast doesn’t support AAC5.1 (only 2 channel).

I have modified the Chromecast.xml file on the plex media server installation within /usr/lib/plexmediaserver/Resources/Profiles. However changes to this file don’t seem to be respected regardless of what I put in it. Are the XML profiles not used when casting from an android device, and if that is the case how do I get plex media server to transcode the AAC5.1 to AC35.1 or similar?