Resetting the logic board and testing and replacing the PRAM battery would have been my first step. Then I would have made sure the firmware was updated and properly updated and rebooted on restart. I am a certified Apple tech and found out a lot of people don't know about other good troubleshooting steps involved for proper diagnostic fixes. Yanking and resetting the RAM along with zapping the PRAM is so a great way to resolve some issues. When it come to problems with the logic board more in depth troubleshooting steps are taken. Best of luck with your next Mac.