[Darryl Ramm]

I don't have experience with your drive (I'm a Samsung Pro M.2 and WD Black M.2 guy). And I avoid any reliance on these small individual enclosures by using Sonnet PCIe expansion chassis (you pay $$$ for Sonnet quality/know how) but with largely dumb PCIe to M.2 adapter cards (just no smarts there at all so a $15 adapter card from low-cost brands like IO Crest or Startech works great, unlike these single slot adapters that have more smarts in them to go Thunderbolt to PCIe and therefore a trusted brand name is likely worth looking for).

I would be surprised if it is overheating. Modern M.2 drives are very good at detecting temperature and throttling performance. But I also can't see if your enclosure has any air vents, the plastic case with no vents even with the heatsink might be a silly design, especially because the controller chips on the M.2 drives get hot, and it's not clear that the heatsink and thermal pad cover that well in this case. Still there are enough single M.2 aluminum enclosures with seemingly good case thermal bonding and some venting. And since the enclosure is suspect I think you are already replacing it.

The way to tell if there are problems is to watch the drive temp, Mac utilities like iStats make it very easy to show/record M.2 drive temps, including those attached via Thunderbolt. My M.2 drives float around a very low 38C much of the time and surprisingly not much more if pushed, they have heatsinks on them and are in a Sonnet Echo Express SE IIIe case with it's very quiet fan. It's spectacular how cool they run. If you start seeing over 70C you likely have issues you want to fix, (separate from any disconnecting).