Cheers for all your help I'll start with the hdmi leads and take it from there.Yes it is mate. That’s the only way I could get 4K @ 60Hz either optical or ARC HDMI from the LG Oled (although if it went via my amp then the shield would Automatically revert to 4K 30Hz.)
re: your amp we’ll need more info than it’s a ‘denon’ get the model number and stick it in google to search what 4K resolutions it can pass through via the output. To be fair your boxes are generic android ones so not sure if they are playing nice with your set up.
I think you have your bases covered: 1. Check what resolution your amp can passthrough 2. Check your HDMI cables are up to spec as well. 3. It could well be your box that isn’t automatically reverting to the available resolutions in your setup.