I found the layout here, but the PC here is older → older CPU with DDR3:
The Board Layout is exactly the same and there is no second mSATA miniPCIe slot.
Don’t you have a J3160 CPU?
For that price you can buy a new SSD: Festplatten & SSDs Solid State Drives (SSD) mit Kapazität (dezimal/SI) ab 240GB, Schnittstelle: mSATA Preisvergleich Geizhals Deutschland
The temperature issue is one thing to be concerned about but the first thing to solve is the increasing error numbers from SMART.
As you don’t have a cable, then I would suggest removing the screw holding the card in and then removing the card and cleaning the contacts with some contact cleaner and a cotton bud.
When the contact cleaner has evaporated off replace the card in the slot and try out again and see if the error still occur.
@arne_f commented that the errors don’t look like they are related directly to the disk itself. If that is the case then the sata interface circuitry on the motherboard could be failing.
As that is non-replaceable then I would suggest confirming that the drive is not the cause of the problems by trying another m-sata drive in the slot. If that also show the same problems then you need to contact the supplier of your mini-pc as suggested by @ms and check the warranty.
The invoice says it’s an Intel Pentium N3700 processor.
I also think it would be a good idea to try it out first and see if it helps.
Nothing unusual when the SATA controller chip gets too hot. It only says that the checksum is not correct. It also could be a cable issue, but not in this case.
You only get these errors when the case is closed, do you?
These chips are operating between -40 to +85°. So much higher than your mSATA disk can handle. And even only when the network cable is plugged in, these chips are (much) hotter than 1Gbps without any traffic. So my advice is to change the network cables from 1-2 to 3-4 and you will see a temperature drop immediately. And as an additional temperature dropper I would use a heatspreader for the mSATA.
As example, but price seems a little bit to high. Just search for “msata heatspreader” via your search engine and you will find the same modell but not this expansive.