I've got "Adjust display refresh rate set" to "On start/stop" and I don't have an option in the GUI to whitelist 1080p 50hz. Have tried a second 1080p 25hz file and it's also not triggering the change in refresh rate for the TV.
Have enabled "Allow double refresh rates" and the TV is now switching to 50hz mode. Haven't had a chance to watch a 25hz video yet but fingers crossed that fixes the problem.
Still having the issue with audio.