I have a late 2016 MacBook Pro running the latest version of OS X Sierra 10.12.6
Ever since I got it, I've been having a problem connecting it to external displays.
Firstly, there is the 32" 4K Seiki Pro, connected via a USB-C cable. Most times when the Mac goes to sleep, the display does not come back until I put the computer back to sleep and wake it up, and then connect the cable when it's woken. Apple Support says this is a known bug but there is not currently a fix.
Then there is the LG UltraFine 5K 27" display for Mac, connected via the included Thunderbolt 3 cable. I got it today. It starts out flickery (the best way to describe it is what an old CRT monitor looks like). But then it looks like it's having a seizure, garbling up pictures and random colors and flickering super bad, and being completely chaotic. I'll try to attach a video to better explain. If the Seiki is connected as well, both monitors do the same thing as long as the LG is connected.