External 4k Samsung Monitor Flickers
I recently purchased a new monitor. It's a 4K 28" Samsung monitor, model U28E850R. It works just fine and looks great when I connected it with a DP cable. However, I noticed the monitor sometimes flickers, which happens randomly. It bothers from time to time and I was thinking returning the monitor. But I later found that if I disable the f.lux, the flicker goes away. It does not flicker all the time. It does not happen right after the monitor is connected. Instead It happens after a while, maybe a few hours, after the monitor has been on. Another thing that I noticed is that almost every time I use the launchpad, the screen flickers. Again, if f.lux is disabled, I don't see the flicker during the launchpad window.
The f.lux upgraded today automatically, but it didn't change the situation. It's a mid 2014 Macbook pro, 15", running on OSX 10.12.4. I have used f.lux for more than a year and have never had the same problem with the Macbook pro's own display. If any additional information is needed, please let me know.
Sometimes the monitor's "on screen display" will allow you to turn "dynamic" or "magic" modes that react badly to changing content. See if there's anything in there that helps?