MP 7,1 Black Screen of Death. Critical External SSD Mounting Bug

[Natalia22]

For the first time in six months, I needed to boot from an external SSD to an Apple SSD. Switching back to my main system was completely impossible.
When I tried to boot, the process stopped 1/3 of the way through the progress bar, after which the computer shuts down and automatically tries again, endlessly.
I tried numerous times to boot into MacOS by selecting the boot disk with the ALT key and from the Apple SSD.

In an attempt to salvage the system for my main daily work, I ran all the diagnostics I could, but to no avail:

Reset SMC/NVRAM
Safe Mode and Disk Utility - The external drive appears disconnected, inactive, and unmounted.
Reinstalling the system - the drive is inactive.
I installed this SSD on another MacPro 7.1 - the same error occurred.
I also installed this SSD into a PCIe MP controller from a different manufacturer.
I installed Sequoia on another external drive. The error doesn't appear immediately, but after several boot-ups from the Apple SSD.
Flashing the DFU for reinstalling BridgeOS.

I finally remembered that I recently updated the system to 15.7.3. So, my last option was to downgrade Sequoia to 15.6. I couldn't reproduce the problem, and everything works fine.

I don't know which version of Sequoia caused this problem, as I haven't booted into an Apple SSD in a long time.
Why didn't I install 15.6 right away? Because I was confident that Sequoia was the most stable operating system, especially for mounting external SSDs. There's a large thread on the forum about a similar issue, but it's not as critical.

Downgrading to 15.6 isn't a solution, but it allows me to continue using the external SSD, so
I immediately reported this critical error to Apple support and disabled automatic update downloads. I also saw several posts from other Mac Pro 7.1 users who, for various reasons, couldn't access 15.7.3, so I decided to describe my experience in detail (using Google Translate).

My Mac Pro 7.1 configurations at the time of the error:

1. Mac OS 15.7.3 on a Samsung 970 EVO Pro 2 TB, Hightpoint controller
2. Sonnet controller for Windows 11

 

[Natalia22]

Another Mac Pro - Windows started updating, but the update failed with an error. Then I couldn't boot from Windows to MacOS; the drives were broken on both drives, the Apple SSD and the external SSD.
Also, when booting Windows on the other SSD, a disk scan started at startup, and then the system booted.
This time, Safe Mode allowed me to reinstall MacOS; the drives were active, but when I rebooted, everything froze at 1/3 of the progress bar. Again, formatting... and so on.

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I described the problem in my first post - I had also previously updated Windows, and afterward, I couldn't boot from the Apple SSD to the external drive.
After re-flashing BridgeOS, installing 15.7.3 several times didn't help. 15.6 boots reliably so far.

 

[Natalia22]

I started by formatting the external drive and installing Tahoe. After rebooting, the progress bar froze again at 1/3 (after about five minutes, the MacOS voice said - ...Press the Key), meaning the installation was complete, but nothing changed on the black screen.

upd: Apple SSD, clean install of 15.6, system freezes 1/3 of the way through loading.
I removed the controller with the external drives, and the system booted correctly. Then I reinstalled the controller, and MacOS boots normally, no issues so far.