Hello, I just got a branch new 2018 15-Inch MacBook Pro (with Radeon Vega 20 graphics) and a Thunderbolt 3 Display (the NEC EA271U). The NEC monitor does not come with a Thunderbolt 3 cable so I got a 1.5ft Nektech Thunderbolt 3 cable from Amazon that is rated for 40Gbps data transfer and 100W PD. I can observe a visible momentary freeze of the picture that occurs roughly every 3 seconds. The freeze happens on both the MacBook internal display and on the external NEC display when the NEC display is connected. It happens regardless of the scaled resolution selected for the NEC display (I always left the internal display running at its default resolution). This happens also when the laptop lid is closed and the external NED monitor is the sole display for the MacBook. The NEC provides 60W of power over the USB-C cable to the MacBook so the MacBook is always charging and always using the Vega 20 graphics. The 60W is less than the peak power usage requirements of the MacBook Pro (covered by the 87W adapter). The issue still happens when I plug in the MacBook to the 87W power adapter (and verify in the System Report that the MacBook is drawing 87W of power from the power adapter as opposed to 60W from the NEC display). The issue happens when Graphics Switching is turned off in Energy Saver. All 4 ports exhibit the problem. I happen to own another 2017 MacBook Pro, which also exhibits the same problem, and a 2018 MacBook Air, which does not have this problem. Based on all this, it does not appear like an issue with the cable or the monitor or the specific laptop. I am running the latest macOS Mojave 10.14.3 on all three laptops. I have tried tweaking Energy Saver and other settings on the monitor, to no effect. Oddly enough, when I return to my laptop and resume it from the beginning sometimes the issue disappears. After switching things around the issue comes back and once there, I am not able to find out a way to get it to go away. I have not been able to figure out under what conditions the issue goes away. Has anyone else experienced anything similar? Here are videos demonstrating the issue: - You can clearly see the picture freeze at .41 seconds. - You can see the picture freeze exactly every 3.15 seconds three times in this 9-second clip: at * 1m 09s 13 * 1m 12s 28 * 1m 15s 43 And for those who might question this being a software issue / glitch, here is a video showing how mouse cursor motion freezes as well, and GPU + CPU utilization on the machine, showing there is no system overload of some sort: Thank you for reading. --- Post Merged, Mar 14, 2019 at 5:41 AM --- So it appears the issue only occurs when unplugging the monitor and plugging it back in while the laptop is running. When cold (re)booting the laptop from power-off or resuming from sleep with the monitor cable already plugged in (and most of the time when plugging the cable in for the first time after a cold boot/resume) the monitor works fine - there are no 3.15 second periodic freezes / stutters. Disconnecting the monitor and reconnecting it again while the laptop is running causes the 3.15 stutters to begin. Every. Single. Time. (The stutters only happen while the external monitor is connected). Note: I do not possess any Thunderbolt 3 to DisplayPort or HDMI adapters to test other connectivity options. I do not have other external monitors in my possession to test either. I am planning on visiting an Apple Store and asking for help to test for this problem using the Apple Store-offered LG monitors) using my laptop and my thunderbolt 3 cable.