I've been having Roku Ultra blanking problems for a year. I've tried ever possible permutation of settings with no improvement. I also purchased 18Gb/sec HDMC2.2 certified cables from three vendors and used them. No improvement.
Today, I finally solved the problem, but it took a$120.00 investment in a Monster Cable Ultimate 27Gb/sec HDMI cable with a lifetime replacement warranty to eliminate obsolescence
The problem is that in 4k 60 Hz OR 30 Hz mode on a 4k Samsung TV, the handshake between the Roku unit and the TV is being corrupted, or the protocol Samsung (and that which others are following) is varying from what Roku demands. 4k Roku devices are not forgiving when it comes to cabling. 18Gb/sec HDMI 2.0/HDMC2.2 certified cables should be sufficient, but they clearly are NOT. I have even had random frequent blanking at the 2k level. In the case of Samsung, Roku tech support does not understand the Samsung Smart Hub requirement as the only source of HDMI/75 Ohm coax inputs. Many tier 1 techs (mostly outsourced from southern India) have no idea that the Smart Hub is fundamental to the very functioning of the Samsung TVs. Without the Smart Hub and it's proprietary cable, you have no inputs. The techs even told me to eliminate the Smart Hub!!!! If I did, I'd turn the TV into a bulky, expensive paperweight!! Roku needs to do a better job in-servicing their customer support, and Roku agents need to stop telling Samsung TV owners to change the advance display settings. These settings allow you to reduce the amount of chroma data relative to luma data....by reducing 4.2.2 to 4.2.0. Do NOT do that! That is not where the problem lies!
You will be unnecessarily reducing the picture quality.
I have had my year-old Roku Ultra on all day long with the 27 GB/sec cable and not even one blanking episode....not one!
And I've been having them 20x per hour from 2-8 seconds in duration, many times ending in the "purple screen of HDMC violation warning death." My problems are now solved.
Why did this happen?
I believe that the existence of the mandatory Smart Hub, a stupid engineering idea by Samsung, relegated the delicate HDMI signal to an unnecessarily long cable and there is invariably some degradation of signal strength. A borderline cable (18Gb/sec) leaves you wide open to packet loss or data corruption, degrading the TV-Roku "handshake." The Digital Rights Management restrictions placed upon your Roku device and your TV are STRICT. If your signal is weakened or degraded, you'll get an HDMC 2.2 protocol warning again and again when blanking gets out of control. You can thank Al Gore for his "work" on DRM in the 1980s-90s to prevent audio and video piracy (sarcasm). If DRM didn't exist, we wouldn't be having this problem. But just like Macrovision wrecked VHS videos in the 80s and 90s, HDMC anti-piracy issues today are making Samsung engineering sloppiness more of a problem for us with our Roku devices.
I hope I have illuminated the problem at hand. To paraphrase Bill Clinton, " it's the cables, stupid."
You can purchase 27Gb/sec Monster HDMI Ultimate cables from Amazon and likely say goodbye to miserable blanking