Randomly shuts down when not connected to an external display.

"It's easier than it looks....

https://outluch.wixsite.com/rmbp-crash

How to fix?

1) reboot with CMD+R pressed.

2) open Terminal

3) csrutil disable

4) reboot in normal mode

5) sudo mv /System/Library/Extensions/AppleThunderboltNHI.kext

/System/Library/Extensions/AppleThunderboltNHI.kext.BAK

6) reboot with CMD+R pressed

7) csrutil enable

8) reboot and forget about problem

We turn off buggy driver, that is for ethernet via thunderbolt. It is possible, you dont need that functionality, like me.

Thanks to:

https://forums.macrumors.com/threads/hel...

and personally to Lukas Kroll, who wrote here in comments about that solution found in that forum."

"Lets try this, download this free app: CoconutBattery.

With the system plugged in with your MagSafe power adapter take a screenshot of the main screen then disconnect the MagSafe adapter and take a second after at least 10 mins of being unplugged. Post them here so we can see them.

I'm suspecting your battery is going here or the battery charging logic has a problem. The issue of the display winking out is related as the system is going into power save mode and the system will then go into deep sleep."

"I can only guess, but to me it sounds like the magnetic sensor that indicates your lid is closed is damaged. It goes into sleep but if your monitor is plugged in, nothing happens (as expected). Problem is that the resistor is on the logic board. It is going to be expansive if you do not know much about soldering and that stuff :-/

A workaround would be to go to settings and change the option when the lid is closed to do nothing"