Mac Mini M2 Time Machine Problems with External SSD using Acasis TBU405 and 4tb WD SN850x

I have two identical Acasis TBU405 external M.2 NVME enclosures, each loaded with a 4tb WD SN850x. Both drives use the APFS Encrypted GUID format.

I use one of these drives as a boot disk for my M2 Mac Mini Pro. Also, it contains all of my data.

The internal 1tb drive was too small when I upgraded: I had about 1.5tb of data on an internal SATA on my 2012 Mac Mini Quad Server, so I created a boot on that external 4tb drive when I bought the M2 Mini. The internal 1tb drive in the new M2 is not used (in fact, when prompted for the password to enable access to the internal data volume I hit "cancel" so that the internal drive is not used at all).

The other Acasis TBU405 with 4tb WD SN850x is called "Time Machine" and is a single volume, used only as my Time Machine backup drive.

However, since day 1, I noticed that my M2 Mini would almost always take several minutes to wake up, and report a Kernel Panic. This occurred on a daily basis.

And I also noticed that the Time Machine volume would often disappear from the Finder, and I often got the message "Disk Not Ejected Properly. Eject 'Time Machine' before turning it off." Whenever this happened, the green light on the Acasis enclosure was still on and the case felt hot (even a long time after disconnecting itself).

I did swap 4k Thunderbolt cables between the enclosures and bought several new ones, assuming faulty cables.

At the behest of Acasis tech support, I finally swapped cases: I opened both enclosures and swapped the Time Machine WD SSD and the Boot/Data Disk WD SSD so they were in opposite Acasis enclosures.

Interestingly, the Time Machine continued to improperly eject on its own and disappear from the finder while the boot SSD worked fine.

On a reboot Time Machine would reappear as it had in the other enclosure, until two or three instances later, it didn't reappear on a reboot: and from then on I couldn't get that volume to appear using any cable or enclosure. The WD SN850x SSD used for backups was fried.

So two weeks ago I sent that drive in for replacement under the warranty, and I just got the brand new WD SN850x yesterday. I excitedly put it into the enclosure, formatted it, designated it as the Time Machine backup destination drive and began the first backup (ETA almost exactly one hour for about 1.5tb). About 45 minutes into the first backup, the drive disconnected and the backup failed. I erased and tried it again, and once again it failed.

Instead of using the Thunderbolt 4 port on the Mini, I attached a USB-A to USB-C cable to the Time Machine drive and left it backing up overnight. That seems to work fine.

I suspect the enclosure and SSD combination just gets too hot and fries the card. But if anybody has any insight: please let me know.

I did turn off the energy saving feature "turn off hard drives when possible" but am afraid to re-connect the external enclosure to Thunderbolt 4 again and fry the card again.

Thank you.