Hello, I'm new with 4k (also new with Octagon SF8008 and Axas His 4k Combo and don't buy it !! ) so I'm not sure about this.
My 1st 4k TV is an Nordmende ND49KS4000, unfortunately it seemed to work with "2160p" setting (with 50 and 60hz and the OSD show 50Hz/60Hz) but after some time (it worked also for an entire week) and randomly the video becomed out of synch (solution: remove the plug and reinsert it). I've contacted the Nordmende service and told me that it's faulty...ok
I've obtained from the reseller a replacement without recurring to the service..but surprice ! the replacement have the same hardware and software version but does not work at all with 2160p (blank screen) and I must choose 25 or 30Hz.
And now OpenVIX (SF8008 5.2 004 release)
that does not have 2160p30 so i must choose 1080p otherwise the screen is blank/black/no signal