NtWaitForSingleObject simply means the thread isn’t running, but instead waiting for a driver or some other thread to complete some work. This could for example be waiting on the graphics driver, or hard disk driver, or something else. In this case, because RenderCommandFence is in there, it looks very much like a graphics driver issue.
I had a very similar problem with my Threadripper 1950X / GTX 1080 computer a while back, which may or may not shed some light on the process you might use to solve the problem.
This is not a problem with the engine, but a problem with one of:
- the graphics drivers
- the graphics card, installation, or cooling
- the OS CPU drivers (yes, there is such a thing! but it’s kind-of hidden and automatically part of OS version updates)
- the CPU, installation, or cooling
- the BIOS support for all the above
For me, it would be even worse than just locking up the computer; it would hard-power-off the system! The problem turned out to be something related to CPU and probably AVX instructions or thermal protection, because after updating BIOS and re-pasting/re-attaching my CPU cooler the second time, it stopped doing it. I think it was BIOS – the first time I did it, nothing worked; when I did it again a year later, it solved the problem. The only other program that would cause this problem was Prime95 – all games would run just fine, as would memtest86, but not UE, and not Prime95!
Debugging these kinds of problems can be super frustrating, because there’s no good way to get signals about “what could be going wrong?” other than changing one thing at a time, and see if it helps. And, like in my BIOS case, if there’s no real solution available yet, then you’re Short On Luck and can’t make forward progress 
So, make sure you have the latest BIOS, make sure you have the latest graphics card drivers, and make sure you have the latest version of the OS. If all of that is tip top, there’s not a whole lot more you can do, unless you want to start tearing the system apart and looking for loose cables or poorly seated heat sinks/blowers.