Have a client's rMBP from Late 2013, no liquid damage or physical damage. Has an SSD, so failing HDD is just about out of the question. Ran Apple's "Extended" Diagnostics via CMD+D on bootup, passed everything (minus battery, but that's expected). Basically, it will lock up about once every...15-30 seconds? Unknown amount of time, I could be doing nothing and it locks up. It's been reinstalled with El Capitan, Mountain Lion, Mavericks, etc. I know it's not a hardware issue because it will work just fine (as it's supposed to) when booted into "Safe Mode." Searched around, found that this was a very big widespread issue, Apple released an EFI update which was supposed to solve the issue. https://support.apple.com/kb/DL1704?viewlocale=en_US&locale=en_US Computer has: Boot ROM Version: MBP111.0138.B16 SMC Version: 2.16f68 Obviously, laptop is well out of warranty, I want to see if I can do anything before deeming it a logic board. Thoughts? I tried putting it back on to OS X Mavericks, the closest copy I could get was 10.9.5 which was supposed to have the EFI update built in, and then the Apple installers won't let me overwrite the EFI update. Can I reflash the EFI?