Mine is doing the same thing. I've been playing the game for a year. But it just started flashing lock screen too and shutting the laptop off. Nothing has changed other then the latest patch from the game. Laptop stays plugged in and is on high performance and I have it set to do nothing when plugged in so the computer never falls asleep till I tell it to. It never struggles with the game. Also laptop is connected to a monitor.
Update 12/10: Did a sleep study in command console and it confirms laptop was going into hibernation. I disabled hibernation thru the command console and now it
