Bitlocker stopped midway during encoding leaving the Drive unaccessible: appears as locked but BitLocker reports it as Fully-Unlocked but No Size

This occurred in a new Dell Optiplex 7000 after a mandatory BIOS upgrade.
It seems that (probably) the new BIOS (DELL SafeBIOS) triggered some silent (no warning) Bitlocker process which affected my old Data Disk which I had installed in the system to create a local copy on a local SSD.

It started like this:

I was copying the data from (D:) on a new local SSD drive.
The File Explorer signaled (D:) with an Yellow Warning (!) and a small padlock. (There was no text or message indicating what was going on or if anything was required of
me).
Disk was accessible but started disappearing after a while. This happened a few times until
Eventually, the Drive became inaccessible appearing (in File
Explorer) as Locked. (big yellow padlock) no other
info (size, etc)

Double-click opens a small warning window:

Bitlocker (D:) The Bitlocker encription on this drive isn’t
compatible with your version of Windows. Try opening the drive using a
newer version of Windows.

Just to be clear, I did not started nor accepted any Bitlocker procedure. This just happened silently, probably triggered by something related to the BIOS upgrade (DELL SafeBIOS).
Also, obviously, there was no key or password generated nor stored in my MS Account or anywhere on the system. See also the troubleshooting steps further down.
This is a Windows 11, fully up to date system.

Trying to troubleshoot, I got these findings:

File Manager shows [D:] without any information except Locked
Disk Manager reports the Disk as healthy, with the correct size, online, RAW and BitLocker Encrypted.
I tried all the hocus-pocus I could find on the internet: moving the
disk on a different SATA port, externally on usb, on a different
Win11 PC, on my old Win10 PC – with consistently the same behaviour.
Even tried on a Linux machine which reported it as locked (no
mention of the locking mechanism)
I tried downgrading the BIOS as well as upgrading back and disabling
SafeBoot. Same behaviour.
From Command Line, BitLocker does not report the disk as locked, unknown size and exits with an error:

manage-bde.exe -status
…
Volume D: []
[Data Volume]

Size:                 Unknown GB
BitLocker Version:    None
Conversion Status:    Fully Decrypted
Percentage Encrypted: 0.0%
ERROR: An error occurred (code 0x80070057):
The parameter is incorrect.

get-bitlockervolume

...
  ComputerName: DESKTOP-KQRSBJB

VolumeType      Mount CapacityGB VolumeStatus   Encryption KeyProtector  Protection
                Point                           Percentage                Status
----------      ----- ---------- ------------   ---------- ------------  ----------
OperatingSystem C:        474.17 FullyDecrypted     0          {}           Off
Data            E:      3,726.01 FullyDecrypted     0          {}           Off
Data            D:          0.00 FullyDecrypted     0          {}           Off
Data            F:      3,815.43 FullyDecrypted     0          {}           Off

manage-bde d: -protectors -get

...

Volume D: [Label Unknown]
All Key Protectors

ERROR: No key protectors found.

the BitLocker logs show the following (BitLocker finalization sweep for D: did not resume after this last line):

TimeCreated  : 12/22/2023 11:32:30 PM
ProviderName : Microsoft-Windows-BitLocker-Driver
Id           : 24665
Message      : BitLocker finalization sweep paused for volume D:.

TimeCreated  : 12/22/2023 11:29:50 PM
ProviderName : Microsoft-Windows-BitLocker-Driver
Id           : 24666
Message      : BitLocker finalization sweep resumed for volume D:.

TimeCreated  : 12/22/2023 11:29:50 PM
ProviderName : Microsoft-Windows-BitLocker-Driver
Id           : 24669
Message      : BitLocker finalization sweep failed for volume D: due to disk I/O error. Check the disk for bad sectors.

Note: HDD was recently checked and also SMART didn’t show any problems.

So, to conclude, it would seem that something (not me, probably the Bios upgrade?) started a BitLocker process which did not complete (last log entry says it paused) leaving the HDD in a weird state (OS thinks it is OK but BitLocked, while BitLocker itself thinks it is unlocked but otherwise unknown)

So, I can’t find a way to approach and recover my data (which I was in the process to backup…)

Please help.