I see that this thread isn't completely dead yet. What I was experiencing was a snow/static screen and a restart, and this would happen whenever I would edit a video. After trying everything I knew of, a reflow of the cpu/gpu is what solved the issue for me. No not in an oven, but using a bottom heater and a hot air station and flux. I previously tried/ruled out
* using a Thunderbolt Display instead of HDMI
* hard drive, including getting the same result with a clean installation of Mojave on external ssd
* memory
* heat/fan
* virus/malware
* power save settings
* pram reset
* diagnostic startup