This problem has caused me to spend a lot of money and waste a lot of time. I ended up replacing my AVR with a brand new Marantz, upgraded HDMI over ethernet cabling and replaced all my local HDMI Cables. (The start of my "fun" was a black screen with audio due to the HDCP 1.4 to 2.2 incompatiblity...then I made upgrades). I have a PlayStation 4 Pro, ChromeCast HD hooked into the AVR and they both stream 4K content flalwessly. I also have the X1 hooked up to the AVR which WILL work under 2160/30. When I turn it up to 2160/60, I get the dreaded BLACK SCREEN intermittently. It is beyond frustrating. My TV is a Samsung sUHD 4K.
Bottom line, this is absolutely a flaw with the Comcast box. So, my recommendation, is to turn down the output of the box (maybe 1080p) until the thing works. My solution will be to switch to Verizon Fios when my contract is up or just cut the cord entirely. Comcast will have you replacing cables until you are broke...why they dont fix this is beyond me.
I am just a customer, playing a customer, disguised as a customer... trying to help those in the same boat.
... View more