I’ve been suffering with alerts almost daily of my slot 2 M.2 drive going over 70c, it’s reached 74c on occasions, slot 1 is usually close to 70c at the same time. Looking at the way the fans are setup in my TVS-H1688x the slot 1 is closer to the fans so would explain this. At normal times they were sitting around mid to high 50s. I have Samsung 980 Pro (1TB) installed and only added the small heat sink which came with the NAS. I use the M.2 drives as read and write cache

I added a Digifast heat sink https://www.amazon.com/Digifast-M-2-2280-Premium-Heatsink/dp/B07ZZFTX17 yesterday and the difference is amazing. They now sit around 43c at normal times and have been peaking around 60c.

If it helps I live in Bangkok and without AC on the ambient temp in the house is 30c. The room with the NAS only has AC when I’m in there, but that can be for 8-10 hours per day. Overnight there is no AC. Hopefully this has solved the overheating issues.