Currently I’ve been running UE4 on an external monitor connected via HDMI. The way Optimus is set up, at least on mine, everything displayed on an external monitor is rendered by the Nvidia GPU, even those apps which are locked by the configuration tool to use the internal card. So it’s nothing to do with switching GPUs
Also, I did indeed have cooling problems in the past, but very recently I did a full clean of the fan and heat sink, and applied new thermal paste, and it’s currently running at temps near the same as when I first bought it. So it’s not temperature, either. Regardless, I have an app that I have programmed to switch to a different power scheme the instant it hits a certain temperature, and neither said app nor the switching has ever once caused a lockup.
Yes, I’ve tried 4.13 since then. In fact, that’s what I had to go back to to get anything done! No problems with 4.13. Also, like I said at the end of my first post, I didn’t even have this problem in the preview 4.14 releases, nor did I have this problem when I would build 4.14 from source. But I have not built from source since the official 4.14 release. I’m reluctant to do it again, because it’s a pain and takes up so much space, (of which I am now limited again since my external HDD leapt off the table to its doom), but I can try if it would help.