So, I may have found the issue. One of my monitors was plugged into a second graphics card. The SLI was already disabled. But moving all monitors to feed off of the single card seems to have resolved the issue. Long working sessions with zero crashes.
I’d had the card/monitor set up for a long while (2+ yrs?) with no previous issues in UE4. So my current assumption is that there is something with the new tech that has made this particular config far more unstable. Just FYI for anyone else who may run into this issue. Hope it helps.