Sometimes the tools don't tell us the full story.
Think of it this way... You're on a call with your friend telling him to meet up with you and your friend is unable to make out what you said, he asks you to repeat when & where. But, he gets the time wrong. So you get angry with your friend when he's an hour late as thats what he thought is what you said. You clearly didn't blame the fault on the poor connection he had in hearing you.
Drive diagnostics are not much different! The fault from your view here is you have a pi$$ poor SSD! But do you?? I bet it's not the SSD thats at fault here.
A very common issue in the Unibody systems (both 13" & 15") is the drive cable breaks down. This is caused by a few different factors depending on the series.
- In the 13" the cable rubs the upper cover underneath The machining of the body can leave some burs which scrape the insulation of the cable. In addition the sharp bends can over time snap the copper lines within the flex cable.
- In the 15" you have the same issue with the rubbing and sharp bends but you also have the risk of the bottom cover bending pressing on the cable. There are two black plastics stand offs which often break from a bang make sure the one nearest the drive is in good shape. If not the cable is likely damaged.
So the answer here is you need to replace the drive cable. If you can I would visit an Apple Store or authorized Apple service center to have them replace the cable. Apple was quietly replacing the cable for free!
I would still replace the cable as a bad cable can damage the drive.
Here's the IFIXIT guide to replace the cable: MacBook Pro 15" Unibody Mid 2012 Hard Drive/IR Sensor Cable Replacement and here's the part you need: MacBook Pro 15" Unibody (Mid 2012) Hard Drive Cable.