First take a look at the Video Settings on the V6 box.
Help&Settings->Settings->Video Output->Video Output Format.
Report what you find here.
First try the Auto Detect.
For your TV the best settings would be 2160p and 2160p 24/25/30fps
Maybe 1080p and 1080p passthrough also if you want the TV to upscale 1080p to 2160p