This is essentially a electrical noise issue. Every contact point on Thunderbolt has two controller chips, which communicate with each other. If either chip crashes or resets, it momentarily auto-disconnects from the Thunderbolt bus. Even in this short time, the disks are signaled to power down. This is essentially what causes the disks to eject messages.

You can try making sure cables are tightly connected.
Move the cables to different ports (do this one at a time, so you have an idea what part of the Thunderbolt bus is causing it)
Make sure no kitty cats are moving the cables, even slightly. ;-)
You can try a different Thunderbolt cable if you have one.
Set display sleep to "never" and uncheck "Put drives to sleep" are also involved in this.

The causes of this are complicated. Even adding a Thunderbolt monitor can trigger disk ejects in some cases.

Let me know if I can point you further. Trial and error is the best way to approach this.

I successfully ran the Firmware update on two Thunderbay 4 enclosures today.

I am running macOS Ventura 13.5.1 as of this week.

I am building my first SoftRAID RAID 1+0 with 4 new WD HDDs that were certified by SoftRAID.

I certified four WD RED PRO 4TB drives a few months back and had them sitting in a new and unused Thunderbay 4 enclosure on a shelf (enclosure #2)

Today I decided I would copy a RAID5 in an existing Thunderbay 4 enclosure (enclosure #1) to a RAID 1+0 in another Thunderbay 4 enclosure (enclosure #2) using the SoftRAID certified WD HDDs.

I built the RAID 1+0 successfully. I split primary and secondary HDDs between my two Tb4 enclosures as suggested by SoftRAID.

Well as soon it was built I started seeing disconnects/reconnects after some time (5 or 10 minutes) of both of the HDD in the Tb4 enclosure (enclosure #2 ) that is daisy chained to Tb4 (enclosure #1) .

I received a warning that it was "disk5" (TLDR: after all of my testing that disk reports as fine)

I decided to re-initialize the disk and verify it. Before the verify could complete I received another warning:

Immediately I thought it's a HDD issue, but they were certified so I was a bit suspicious of that warning.

To narrow it down further I moved "disk5" to a different slot in enclosure #2 and tried again. I received the same warning and issue - so it's not the slot.

I then decided it might be best to delete the RAID 1+0 and start over.

I deleted it and re-initialized all four HDDs which completed without error.

Thinking it could be the cable arrangement, I moved the daisy chained TB cable directly to the second USB-C port on my iMac to test if that might be an issue.

I then ran verify again, on the same disk,  and it's running without issue for an hour now.

My question is:

1. Can I setup two Tb4 enclosures where one is the primary and the other is the secondary and daisy chain from one to the other?

During this entire time I didn't touch any cables because I am aware they are not the most stabile connections. That should rule out that possibility.

It also seems it's not a damaged cable as I am using the same cable that was daisy chained and the verify is progressing fine.

The only other possibility is one of the ports is bad on the enclosure. I will check that, but would like feedback first on the question first.

Thank you