Xg1v4 4K resolution not working when using A/V receiver
I recently upgraded my TV to a 4K-compatible TV (LG OLED65CXPUA). I also use an A/V receiver that I have confirmed is capable of 4K pass through (Sony STR DN-1040). I use HDMI cables that are certified for 4K throughput. I have the TV connected to the receiver via the ARC-capable HDMI port on the TV and the ARC-capable output port on the receiver. The X1 XG1v4 is, of course, connected to the receiver via HDMI as well.
The X1 box doesn't recognize the 4K compatibility of my setup. Oddly (as an aside), despite selecting LG as the brand during remote pairing, the X1 box thinks the TV is a Sony. If I connect the HDMI cable from the TV directly to the X1 box, the box then recognizes the 4K compatibility and I am able to set 4K resolution in the video display settings for the XG1v4 box. But then I'm stuck with the internal TV speakers.
So the issue is clearly the X1 box not recognizing the 4K compatibility of the TV via the 4K pass through of the receiver. And, thus, the video display settings of the XG1v4 limits me to 1080p HD as the best possible setting. Is there a way to fix this issue?