It's just one of life's little annoyances.
You tune to DIRECTV channel 104, 105 or 106 to watch some of that sweet, sweet 4K content and what happens?
You get a black screen for 3-5 seconds, and eventually your 4K content shows up. I mean, it's the very definition of "first world problem," but let's be honest it's also kind of a drag. You spend that time wondering how it is that your $1,000+ TV has this sort of problem and you want to blame DIRECTV. Except you can't, not without evidence.
Truth is it isn't DIRECTV's fault, although blaming your TV isn't 100% fair either. The real problem is actually content protection. See, when you change to a 4K channel, advanced algorithms spring into place, enacting all the mathematical protections of something called "HDCP 2.2," the latest and as-yet-unbreakable version of the content protection that's in every HDMI cable. See, HDMI was never about giving you a nice, clean, one-wire solution for your connections. It was always about making sure that you couldn't copy that nice clean pristine HD feed. Here's where I told you all about it
. HDCP takes a ride on every HDMI cable, and it brings with it a lot of math that's required of both your TV and your DVR.
When there's a resolution change as well as a change in the level of content protection, as there is when you change to a 4K channel, your TV and DVR begin a delicate dance to make sure that it's ok to send a video signal. The TV has to essentially promise that it's a TV and not some sort of insidious video-copying device. The DVR has to essentially promise that it has permission from the people who created the program to actually show it. It takes time for all of this to happen, and both sides are limited by their processing power. So right there, that's why you get that black screen.
This black-screen tango used to be pretty common in the early days of HD too, and for the same reason. As you changed the channel, long black pauses used to be the norm, until TVs and DVRs got fast enough to handle them. We're seeing the same thing here, and eventually if 4K actually takes off you'll see TVs and other equipment that are fast enough to handle HDCP 2.2 without much fuss and bother.
Until then, take the time to meditate or enjoy the view out the window while the black screen is sitting there. I promise your 4K picture will be there soon.