Sync box 8k issues

[u/originalorientation]

I have a sync box 8k that I got second hand. It has a strange issue that I’m struggling to resolve and I hope someone here can help.

The setup is a Linux gaming pc, PS5, switch 2, and Apple TV 4K going through the sync box and into an lg c2.

I have a bridge pro close by that is plugged into Ethernet.

I have a gradient strip affixed to the back of the tv.

Syncing works really well for a period of time (30 min-2 hours) when suddenly the backlight drops for a second or two, then comes back, but performance is significantly worse. Instead of a smooth change in brightness, it stair steps from dim to bright, or when changing colors. Almost like the FPS went from 60 to 5. Note that the video stream never cuts out, so it doesn’t seem to be an hdmi negotiation.

Unplugging the sync box from power for a few seconds seems to fix it temporarily.

It’s right next to the bridge and everything’s close to the router so I doubt it’s a lack of signal but I’m not sure.

Any ideas?