Do you have your Kodi desktop resolution set to 4K? Because you shouldn’t do that either.
Not easily I’m afraid
No, just FullHD. On 4K Kodi is unstable and crashes.
Never mind, I’ll try to google how these ports differ, and experiment with settings. Thank you for the info!
If your desktop resolution is 1080p and Adjust Refresh Rate is set to Off, then everything Kodi outputs will be at 1080p resolution, and at a fixed refresh rate. That’s just how Kodi works. It can still decode a 4K video and play it, but the signal it sends to the television will be downscaled to 1080p.
That’s the reason why the screen doesn’t go black: the HDMI connection can handle a 1080p signal but not a 4K signal. When you actually send 4K to the TV, it can’t handle it, and the picture drops out. Why it can’t handle it is a whole other question.
I had that TV (gave it to my mum) bought a LG cx 65 inch and now that is real HDR. the KS7000 doesn’t have real HDR in my opinion. I had it on HDR setting for ages thinking I was watching HDR but it wasn’t until I bought the new TV that I could see what real HDR was.
So, I’ve whitelisted only the required resolutions/frequencies, and the problem remains. Moreover, HDMI port 4 also stopped working. Only HDMI 3 works, but it constantly loses signal. It happens even on 1080p. Only videos without HDR don’t cause loss of HDMI signal.
I’ve ordered a new premium HDMI 2.1 cable with gold-plated contacts, and I’m hoping it was the cable’s fault, not the One Connect box which costs around $200. Tomorrow I’ll be able to check and let you know if it helps.
Is the One Connect box something that sits between the Vero and the TV? If so, can you (just as a quick experiment) try bypassing it and connect direct to the television? If that works, then it isolates the problem to the box or one of the connecting cables.
Also, while the chances of this helping are rather small, you might try turning on “force 4:2:2 colour subsampling” in Settings / System / Display. There’s a slight chance that might stabilise the 4K HDMI connection (meaning you can then set Adjust Refresh Rate to the correct value).
Yes, it is a box which sits under the TV and allows to plug all devices to it without the need to connect a lot of cables to the TV. But, unfortunately, the TV itself doesn’t have HDMI ports, only this One Connect box.
You were right, this setting helped, and now I have a stable signal on all four ports! I found a topic with the same problem and solution:
What this 4:2:2 actually means? Is it worse in quality? My TV still shows HDR logo, and the colours seem to be OK (at least the Netflix logo is bright red, not pale orange as before).
In theory, it is worse quality than 4:4:4 but since the original video would be 4:2:0 you won’t see a difference.
4:2:2 is carried at a lower bitrate than 4:4:4 so it’s easier for cables and equipment to pass.
Does 4:2:2 subsampling require some extra GPU or CPU work?
At the margin, yes, but it’s handled by the HDMI chip.
I know you know this, Graham, but for the benefit of eugeno …
The actual video file is always stored in 4:2:0 format - that means you have luminance (brightness) data for every pixel in the picture, but colour information (chroma) only for one pixel in every four. (This is a useful way to store compressed video, because the eye is better at detecting fine detail in brightness variations, and not so good at detecting fine colour variations).
So, 4:2:0 is the raw format in the file, where we have colour data for 1 pixel in 4. 4:2:2 means we have colour information for half the pixels. 4:4:4 means we have colour information for all the pixels.
In order to actually display the image on the screen, something somewhere along the line has to calculate colour information for all the pixels that we don’t have colour info for in the original video file. This is done by interpolating between the colour pixels that we do know about; the process is called “chroma upsampling”.
If we send 4:2:0 to the screen, then the television would be doing all of the upsampling to convert to 4:4:4. If we send 4:4:4 to the TV, then the player is doing all of the upsampling before the signal reaches the TV. If we send 4:2:2 to the TV, then the player is doing half of the upsampling, and the TV is completing the process.
Assuming that each device is using the same upsampling algorithm, the end result on the screen should be exactly the same in all three cases. Occasionally, some devices do a better job of chroma upsampling than others - for example my Nvidia Shield TV does an incredibly bad job of it, and if you can get the TV to do it instead, the image looks better. But most of the time it doesn’t make any difference which device does it - the end result looks the same.
Assuming you are talking about a 24Hz signal, then 4:2:2 12-bit is indeed a bit less bandwidth than 4:4:4 10-bit. Also, 4:4:4 10-bit is a sightly unusual format that some TVs (not many) aren’t comfortable with.
It should be said that the same setting also makes the Vero output 4:2:2 for 50Hz and 60Hz videos, and 4:2:2 12-bit uses considerably more bandwidth than the default 4:2:0 10-bit does at 50 or 60Hz. TVs may or may not be more comfortable with that - you need to experiment.
The fact that this setting helps doesn’t completely rule out a problem with an HDMI cable or the Connect box - it could be that using 4:2:2 reduces the bandwidth just enough to allow the signal to get through, but that a better connection would allow 4:4:4. If the TV supports 4K/50Hz or 4K/60Hz modes then they may work better with a new cable.
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Thank you @angry.sardine for such detailed information! My understanding of how it works is much better now. Tomorrow I’ll get the new cable and test it.
You are right — some HDR videos from Youtube also cause signal stuttering even with forced 4:2:2 subsampling. So all hope for the cable 
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No worries. 
Are they videos that are 50 or 60 frames per second? If so, there’s a slight chance they may actually run better with 4:2:2 subsampling turned off - but only a very slight chance.
Take a photo of what the problems looks like if you can. How does it differ from the previous version? There is never a need to spend $200 on a cable, just buy a decent quality latest version HDMI cable of the required length.
It’s his One Connect box that costs $200, not the cable.
You would be even more mad to spend $200 on a new one connect box in my opinion. I suspect it is the panel not an issue.
Yes, they are mostly run at 60 fps. But with 4:2:2 subsampling turned off they run even worse — I mean HDMI signal is lost more frequently.
I’m not going to buy a new One Connect box, especially now, when 4:2:2 subsampling seems to fix the issue, at least for 24 fps videos. And this indeed would be mad to spend $200 on a device without being sure that it is the bottleneck.