Update - I changed the "what happens when you close the lid" setting and haven't experience the problem in the last 1.5 days of heavy use, plugged in and not plugged in. It is now set to "do nothing". This makes me think that there's a sensor misfiring (probably
a driver - if it was the hardware, you'd see more bizarre behavior) and perceiving a hand motion as a lid close.
Wild speculation - anyone else that is experiencing this wear a smart watch? What if it's picking up something from a smart watch close to the sensor and thinking that is a lid close? Total speculation, but if sleep on lid close is the problem, then it's got
to be picking up the signal somewhere.
Last thought, I'm not returning as I do not have concerns about having to replace this with a refurb. I come from the PC world. "new" laptops come off an assembly line and receive a baseline quality check. Refurbs for reputable manufacturers receive a much
more thorough check because they are refurbs. Just food for thought.