Sony Soundbar issues

Hi all, have put this question on the Sony Community a few days ago but so far no replies so will try here:

My gear is:

BDPS6700 Blu Ray player with 4K Upscale

KD-55X8500C 2015 Android 4K TV

HT-RT3 Sound Bar (5.1 Surround)

The soundbar generally works well, can hear the 5.1 doing its thing if I watch a TV channel with 5.1 encoding.

I run into an issue when I am playing a blu-ray movie, when I start a disc all the beginning stuff works but soon as it hits the main movie the sound stops and I have to run the sound through the TV.

The setup is Blu Ray player -> (HDMI) -> TV -> (HDMI) Sound Bar.

I have got the latest firmware running on everything, I have updated the TV to use "enhanced" hdmi on the port the blu-ray player is connected to.

I've tried a few things on the TV like setting the Digital output to AUTO 1 and 2, even tried on the blu-ray player getting it to convert DTS to dolby digital with no luck.

Has anyone got any ideas or able to point me in the right direction? or it just better I take it back to JB Hifi?

Thanks.