My impression from the user forums is that all NVMe SSDs run hot. That's why they need heatsinks.
Also, if you are using a USB-NVMe adapter, be aware that certain bridges have stability issues:
https://forums.anandtech.com/threads/stable-nvme-usb-adapter.2572973/Personally I would set up a test jig using a PCIe card plus an extension cable. The cable would be connected to a passive adapter which would ideally provide access to both sides of the SSD. I would then attach stick-on heatsinks to the major heat affected ICs.