Problem

After upgrading to MacOS Sierra on a Mid-2012 Retina MacBook Pro with an aftermarket OWC SSD, the “folder with question mark” icon appears upon boot, and intermittent pinwheels cause hard-resets/crashes — especially coming back from sleep mode. System heats up during charging.

Things Tried That Did Not Work

• PRAM Reset
• SMC Reset
• First Aid with Disk Utility
• Flashed the OWC SSD to latest firmware
• Disabled FileVault
• Clean install of Sierra
• Opened up the laptop and reseated the OWC SSD
• Disabled the “put hard disks to sleep when possible” check box in the Power section of System Preferences
• Changed “hibernatemode” value from 3 to 0.
• Disabled Wake for WiFi, Power Nap and Automatic Graphics Switching
• Removed the OWC drive, cleaned the contacts with alcohol and placed a small pad to apply pressure to the contacts to ensure good contact.
• Secure-erased the SSD

What Finally Did Work

Replaced the OWC drive with a new 480MB mSATA drive (MDMS-BP4e-512) and a model-specific adapter.

The adapter and drive together are a bit taller than the original equipment.  There appears to be a slight clearance issue.  The drive fits right up against the bottom panel and pushes it out slightly, about~0.2mm, after reassembly.  It’s not enough to notice unless you’re looking for it, but the adapter could be improved with a slimmer profile.  For half the cost of a more perfect fit, it’s a satisfactory option.

So much for the fabled longevity of SSD‘s — the OWC lasted about three years.