Samsung HW-T650 soundbar automatically changing inputs

[CaptainKirk7]

So I've recently gotten a new smart fire tv and I've connected it to the soundbar via hdmi arc. I also have my soundbar connected to my PC via a digital optical cable. 

With the new TV, whenever I try and switch from ARC to OPTICAL on my soundbar, the bar automatically switches it back to the HDMI arc. Is there anyway to stop this from happening?

[Pydr]

Same problem. It´s a pitty, Samsung is not trying to answer or help ...