Wakes from sleep briefly then shuts down or nothing
This is a client's MBP Retina 13" mid 2014 that suddenly started doing this last week. If you let it go or make it sleep by the menu or close the cover and wake within 10 seconds it's fine, but longer than that this is what happens:
Either 1) it will wake for a fraction of a second, you can see the screen during that time, and then it goes black, meaning off as it will not come back up unless you start it up with the Power button until the chime and the logo appears.
Or 2) nothing at all, no wake and you need to press the power button until the chime is heard and the Apple menu appears to restart the machine. If you let go the power before the logo appears, nothing. Number 2 is more frequent than 1.
I have researched the Internet and tried everything I could find but nothing. I have reinstalled El Capitan on top on the current install, nothing. I have backed up and did a clean install: same. This has an SSD drive screwed on the logic board, and the RAM is soldered on. But First Aid says drive is OK and diagnostics check also says everything is OK.
I cannot get this MBP to output to an external screen even when booted up. Tried with video out and HDMI. Put thing to sleep briefly, plug in cable and wake, remove and plug in cable, nothing.
Any ideas before I tell this lady to live with it? Because I am not convinced a new main board will fix this issue at this time. For all I know it could be related to a faulty sleep detector in the case.