fsck_apfs reports error: (oid 0x1c8eeb) om: btn: invalid o_type (0x40000002, expected 0x40000003)

[chriskuku]

macOS BigSur 11.7.10

My 5TB WD Elements 2620 went south in a way that some containers are visible and are being mount while the container that contains the backup, cannot be activated. It is not getting mounted.

I tried and fsck_apfs /dev/disk2s2

$ sudo fsck_apfs  /dev/disk2s2

** Checking the container superblock.
   Checking the checkpoint with transaction ID 263004.
** Checking the space manager.
** Checking the space manager free queue trees.
** Checking the object map.
** Checking volume.
** Checking the APFS volume superblock.
   The volume BackupNeu was formatted by diskmanagement (1677.141.3.7.2) and last modified by apfs_kext (1677.141.3.7.2).
** Checking the object map.
error: (oid 0x1c8eeb) om: btn: invalid o_type (0x40000002, expected 0x40000003)
   Object map is invalid.
** The volume /dev/disk2s2 could not be verified completely.

I ran the latest drat 0.1.3 --container /dev/disk2s2 inspect and it looked as if there were no errors.

Do I have a chance to get it repaired using drat or are there other recommendations?
The diskk is encrypted. When I post the full output of the drat inspect command here with all the information (UUID etc.) would it be advisable to obfuscate the information? Anyway, I'll append the information below.

[t.txt](https://github.com/user-attachments/files/17797340/t.txt)