Need help with surround sound system

Hello all,
We have an old Yamaha rx-v571 system (it was already pre-installed when we bought our house last year). At the time, we had a Toshiba 65-inch 4k tv and I had each of the three HDMI ports filled with the cable box, 4K Blu-ray and the Yamaha unit. Regardless of which was selected (cable or Blu-ray), all audio played through the system. Sound was great, I could switch between all of the preset configurations (jazz hall, spectacle, game room, etc).

Fast forward to a week ago, we bought a 75-inch LG 4K tv. One of the HDMI ports says ARC, so I connect the Yamaha to that one. I have audio, and can hear any of the other devices (cable, Blu-ray) as well, so I’m thinking “ok great, now let’s check out Solo”. However, when I try to switch up the configuration to one that better suits what I’m watching (spectacle, jazz hall, etc), I can hear a change in the background sound, same as I used to before, but the voice/dialogue of whatever I’m watching drops almost completely.

Is there a workaround for this? I would think, even though it’s an older system, since I’m getting direct sound from the default ARC selection that everything should be fine. Any suggestions would be appreciated, thanks in advance.

EDIT: Now that I’m looking at it again, when it’s connected to the ARC port the system defaults to “straight” and it seems like I’m only getting sound out of the front speakers. Then again, it could be due to what I’m watching.

I always find HD ARC a finicky endeavour, is the cable compliant?

Secondly, I will never mess with the sound presets since audio, just like picture, is an exact science and shouldn't be subjective when properly calibrated. If you're getting stereo sound, check what signal the media you're watching is outputting. There are plenty of blu rays only encoded in DTS-HD Master Audio 2.0 for example. For 2.0 sources, you should never "fake" expand them to 5.1 unless it's a Pro Logic/DPL II encoded audio. Hope that helps!