LH tv 75UD76 sound bar inactivity auto shut-off

[Boddek]

My TV model 75UH76. I have Bose sound bar connected thru HDMI and headphones connected through optical cable. If I want to use headphones together with the speakers, the only setting option to use is "optical sound out with TV speakers". When I switch to this mode, the connected sound bar becomes inactive and makes the TV turn-off itself automatically in 15 minutes. Is there a way to turn off automatic inactivity shut-off? I tried everything possible, read all the related forums, instructions etc. and nothing works.

 

[JayCee]

Have you tried turning off the Soundbar with it’s own remote?

 

[Boddek]

yes, when turning off sound bar, the TV turns off also