That would depend exactly what the problem is.
If the channels streamed to your box are the issue, they are glitching because of errors in the stream. If the isn't a problem with the phone line or BT's equipment, then it good shielded Ethernet cabling can be key to solving this like using the cable that comes with the box. However stream errors do not normally present the way you are describing. you normally get Glitches like bad macroblocks or lines that are can be just out of place off colour to the loosing whole picture is a mess of macrobock or loose it all together, the audio can dropout or glitch too, the glitches can be accompanied by the ip6023 error.
The second possible issue, assuming a good error free stream, would the de-interlacing performed by the box. it doesn't flicker but there could be some interlacing jitter ( typically de-interlacing the picture lines in the wrong order, people often mistake this for flicker). This would cause the graphics or the entire picture to move up and down slightly. Admittedly the BT uhd box does not do the best de-interlacing but it's normally plenty good enough and never normally that bad. You have reset the box so that should have reset the picture processing within the box. I would try setting the box to 1080i ( i'm not sure if this actually disables the boxes picture processing) but this does enable your TV to handle the de-interlacing on HD channels.
Third possible issue the broadcast or some local BT equipment. nothing we can do here.
4th Issue, your TV, Most tv's have soo many options to adjust the picture, and other picture processing option to reek havoc in the wrong hands. some signals can make the processing on certain TV's do some really stupid things. with 1080i if you have options to set the de-intelacing mode you want video or bob, if the are only 2 options the opposite one to film. if you are feeding your TV with 1080p, or UHD it should be off or whatever your TV 's equivlent of off is. With UHD or 1080p some tv's Game mode can diable all the picture processing too, even fix lipsync issues too, getting your tv to act more like a monitor.
I suspect 2 or 4. and I really hope it's number 2. I'm not entirly sure of the openreach WBC TV services layout or where the final iptv broadcast takes place, but if the picture is encoded somewhat locally at a headend, your local headend could be causeing simlar issue to issue 2.
All I can say is best of luck.
He already said it's BT sports Europe and flickering, I recon it's de-interlacing judder, from the boxes cheap de-interlacing and scaling, not doing the best job scaling the picture to 2160p.
Anyhow the issue described their was aparent today on BT sport UHD , not because of the TV but because BT use 4 HD feeds to make up the UHD picture and they kept sliping out of sync, there was a horisontal and vertical tearing at the boarders of the feed.
Make sure the software on your Samsung 4K Tv is up-to-date.
Also if you are trying one of the UHD settings have you tried both the 8bit and 10bit settings in case the 10bit one isn't fully supported.
If you post the model # of your Samsung TV there might be more somebody who knows more about this issue.