Help! Partition unmounts at random in el capitan

Ok, this is a difficult one: Long story short, My partition keeps unmounting. This all started when my system froze when an iphone call was redirected to my mac while I was playing Civilization 5. I powered down, but when I booted up I was welcomed to the flashing grey folder with a "?" Mark. Went through the standard troubleshooting steps, assumed it was the hard disk so I had it replaced with a Transcendence SSD. Installed the SSD, installed os x, upgraded to El Capitan. Was able to access my information on the old disk with an external mount via usb. Moved the data over (videos, pictures, etc) and all seemed to be well. I even made a time capsule backup on a 3rd ext. HD. Then, while running an app, (Civ 5 :/ ), the system crashed again. 2nd time around was more difficult but managed to get back to El Capitan via Time Capsule Restore. It lasted the day. This time, after closing the macbook, I opened it up sometime later and was greeted to a reboot and our old friend the "?" mark folder. Any ideas on how to resolve this would be greatly appreciated. Troubleshooting steps attempted are listed below: Mac details: Macbook Pro mid 2012 13", 4gb ram, 512gb Transcend SSD Troubleshooting steps: After 1st crash with old apple 512gb 3.5" IHDD: Booted into internet recovery mode Ran disk utility: unable to verify or repair disk nor volume (option greyed out) Switched to terminal and ran disk utility: same results at this point, since my data was not backed up, I bought an SSD and switched HDD (see story above) After 2nd crash: Ran disk utility: unable to verify or repair disk volume(option greyed out) Attempted to erase disk: process froze. Attempted delete and remake partition (several times): process froz at "waiting for disk to reappear). Ran same steps through terminal: same results as above Partition was set to: Disk0 - FDisk_partition_scheme, disk0s1 - 0xEE Began researching os x terminal commands and searching for similar situations. Installed mountain lion on a slow 16gb usb to run TestDisk: no results Played with Fdisk and fsck commands: no results Learned about GUID Partition Table Attempted to change partition from 1 to 2 partitions with GUID and back via disk utility, and fdisk: no results. Called Apple support and explained the situation. They think it is the logic board. I am skeptical because I can access the The old HDD and the SSD through usb ports with no issues. They suggest to bring it in. I live in Japan and due to location, that option is difficult Out of desperation, i resize to 16 partitions.... Success!!!!!! Repartition complete (no idea why) Reinstalled Mountain Lion: success Upgrade to El Capitan: success Restore data from Time machine backup: success System seems to be operating normally. Download some tv shows, organize photos, browse web. System is running fast. Shutdown mac and power up a couple of times: no issues Running system for a couple of hours, then close the lid (assuming it enters sleep mode): return to the grey "?"mark folder :( My apologies for the novel. I will be forever grateful for anyone who can point me to a solution other than sending it in to Apple support.