External monitor flicker / signal loss
I have a Samsung 28" U28E590 4K Display and a 13" MacBook Pro with Touch Bar (Intel Iris 550 1536 MB Graphics). I have a dongle for HDMI output.
The problem is that the external monitor flickers, displays white noise and sometimes cuts out completely. I've tried SMC reset and buying a new HDMI cable, but the issue persists.
How do I resolve the issue?
I've had a support case at Apple for over a year about this issue. They finally answered that it's a software issue and they are looking into it.
We have spent a lot of money in our business on original adapters and good technics to have a good setup. Several of our MBPs with USB have this flickering problem on 1 of the 2 screens (always the screen you attached last).
I really hope that Apple can find this seriously soon or they will probably lose more customers. We are not very satisfied. After all, we have spent lots of money at Apple to get this sorted with no result more than an answer 1 year after - the answer "it's an Apple software problem".
I just had this issue with a 2016 MBP and a Samsung 28" U28E590 Display. Tried a bunch of things, but what seemed to work was switching the monitor to use to HBR1.
The setting was in the monitor's menu under System -> DisplayPort Ver.
As soon as I switched it, the intermittent flickering stopped.
I have the same 4k monitors (Samsung 28" U28E590 Display) and just purchased a 2017 MBP 15" 2.9 GHz Intel Core i7. I experienced rapid flickering when hooking up HDMI to the Apple Multiport Adapter (via it's HDMI port), after a bit of research on that monitor I found that it's best supported by the DisplayPort and that the HDMI was extremely unreliable with most new MBP's. I then went out and purchased a USB-C to Display port adapter (you should have gotten a DisplayPort cable with your monitor) and voila! No more flicker. The picture quality even seems a bit better. I am not ordering 2 new USB-C to DisplayPort cables which, based on the test with the adapter, should work.
Here is what I've ordered: https://www.amazon.com/DisplayPort-ITANDA-Thunderbolt-Compatible-ChromeBook/dp/B074GVQBY2/ref=sr_1_1_sspa?ie=UTF8&qid=1513745117&sr=8-1-spons&keywords=usb-c+to+displayport&psc=1