Draining was to take all power out of the system, then boot. But hey was thinking the emmc myself, very unusual for this to behave in this way..
But here is your most important option right now as mentioned.
Backup your console fully right now to save you trust me. If the emmc is dying and u dont backup you have paperweight without backup..
Backup Biskeys/system keys. > with LockPickRCM Payload.
Backup rawnand (emmc) > with Hekate
Backup Boot 0 > with Hekate
Backup Boot 1 > with Hekate
Please backup all of the mentioned above. and make sure you have solid backups and even copy of the backups..
Replacement modules (Emmc Modules can be found quite easily online)
You will need to Format correctly, Use Gpt Restore payload to CorrectlySet this, and then should be able to run hekate to restore nand. May use hacdiskmount to check partitions/structure and biskeys are linked.
I wish you goodluck. NOW BACK THAT CONSOLE UP!~!!
Edit: Just a thought, you never overclocked or underclocked did you ? That i think is held on the SD card in a config, try erase sd card and install just the cfw on it. And see if its better.
If u did not or it does not work then yes its probally the Emmc, Or Ram