It seems that you're receiving a warning because your drive's Available Reserved Space, measured by the E8 SMART attribute, has been depleted.
The reserved space of your SSD is a hidden area which is used to replace worn out memory blocks. Once this area has been used up, you will begin to notice your E9 Media Wear Out indicator slowly going down from 100 to, eventually, zero.
Possible causes for this range from normal usage over time to manually using trim far too often. Looking at all your SMART attributes, your drive looks healthy and should not fail any time soon. To be safe, you may continue monitoring it's health using the https://downloadcenter.intel.com/download/26776/Intel-Solid-State-Drive-Toolbox Intel® Solid State Drive Toolbox, or by keeping an eye on it's E9 SMART attribute.
If this resolves your doubts, or if you have any additional questions, please let us know.
The PC this came from is hardly used, it's the mother in laws machine and TRIM is only set to trigger once a week via the Intel SSD Toolbox (as per default settings).
This SSD is actually a replacement for the original Intel SSD which had exactly the same error. It was replaced under warranty, but the original replacement is now out of warranty so I've had to purchase the new replacement. I spent all weekend getting her data across due to no cloning application wanting to touch the drive (even g4u) with the errors it was throwing up. But got there in the end!
So, this is the third Intel SSD I've installed in this machine, the first two dying with the same error. Is there something else that could be doing this I need to look at? All my other machines have Intel SSDs and I have much older drives than hers still in use.
I actually switches families this time (since it wasn't covered under warranty) and went to a SSDSC2BB240G701. Hopefully I'm not on here in another couple of years with the same issue. Don't want to sacrifice a 4th SSD to this PC!
This is a very odd issue.
There is nothing on these SMART details to suggest anything wrong with the drive, other than it's reserve space having been used up. We verified and there is no write amplification being shown, nor any other issues.
Is there any chance that this drive has been periodically defragmented? This would be one explanation.
Regardless, the Intel® SSD DC S3520 Series is a very high endurance model, and you should not have any new issues for a long time.