Issue on Chunk when packing backup

Hello,
I was able to create a backup point (first pass) but was unable to pack it.

sudo -u www-data php /var/www/html/nextcloud/occ backup:point:list

returns:

- retreiving data from local
 > found RestoringPoint 20220112111713-full-lQoHZL8oq5FL82h
- retreiving data from external:7
 +---------------------------------------+---------------------+-----------+----------+--------+---------+---------------------------------+----------+-------------+--+
| Restoring Point                       | Date                | NC        | Database | Parent | Comment | Status                          | Instance | Health      |  |
+---------------------------------------+---------------------+-----------+----------+--------+---------+---------------------------------+----------+-------------+--+
| L 20220112111713-full-lQoHZL8oq5FL82h | 2022-01-12 11:17:13 | 23.0.0.10 | mysql    |        |         | compressed,encrypted,processing | local    | not checked |  |
+---------------------------------------+---------------------+-----------+----------+--------+---------+---------------------------------+----------+-------------+--+

sudo -u www-data php /var/www/html/nextcloud/occ backup:point:pack 20220112111713-full-lQoHZL8oq5FL82h

returns

> lock and set status to processing
> Browsing RestoringData data
> Packing RestoringChunk data-8fe2fa17-1e3e-4468-adaa-e9c32fc63a56: already packed
> Packing RestoringChunk data-efcd92ff-c13c-4f6c-a112-876df9bd8596: already packed
> Packing RestoringChunk data-27b93faf-f732-4d39-a2dd-3d53ce29fab0: already packed
> Packing RestoringChunk data-91d503a3-9813-448a-ab12-98431dd08b7f: already packed
> Packing RestoringChunk data-fd0494c5-3326-4104-be49-62e3cfa8f73d: already packed
> Packing RestoringChunk data-401b9a76-1bff-4285-8ad1-755d02847697: already packed
> Packing RestoringChunk data-57d12a73-84ed-417b-9800-dd09016a1318: proceeding
    * copying chunk to temp file /tmp/phpJSSODC: ok
    * compressing /tmp/phpJSSODC: /tmp/phpCcu5LD
    * spliting /tmp/phpCcu5LD in parts: 31 part(s) 
    * encrypting each part
    . encrypting /tmp/phpx2TsrD: /tmp/phpVSrTXE, aes-256-gcm
    . encrypting /tmp/phpORP7uG: /tmp/phpjkztUF, aes-256-gcm
    . encrypting /tmp/phpbvuZ6D: /tmp/phpnw5WAF, aes-256-gcm
    . encrypting /tmp/phpnMVFTC: /tmp/phpiop55C, aes-256-gcm
    . encrypting /tmp/phpIXYXMF: /tmp/phpCtMXiF, aes-256-gcm
    . encrypting /tmp/php1T6SLE: /tmp/phpIO16vG, aes-256-gcm
    . encrypting /tmp/phpM9E8bF: /tmp/phpb6IGiD, aes-256-gcm
    . encrypting /tmp/phpfc8FLC: /tmp/phpRvw0FE, aes-256-gcm
    . encrypting /tmp/phpA2QSwE: /tmp/phpTkUiJC, aes-256-gcm
    . encrypting /tmp/phpJFNKOC: /tmp/phpJKvatC, aes-256-gcm
    . encrypting /tmp/phpfCDhWF: /tmp/phpqG4nED, aes-256-gcm
    . encrypting /tmp/phpoCkDGE: /tmp/phpwvqvfG, aes-256-gcm
    . encrypting /tmp/php29kY9F: /tmp/phplovyqC, aes-256-gcm
    . encrypting /tmp/phplEkgpE: /tmp/phpskvufE, aes-256-gcm
    . encrypting /tmp/phpUDuOKC: /tmp/phpOogveC, aes-256-gcm
    . encrypting /tmp/php7iDYWF: /tmp/phpeC4KkG, aes-256-gcm
    . encrypting /tmp/phppMLtpC: /tmp/php4wzB6E, aes-256-gcm
    . encrypting /tmp/php1pC6oC: /tmp/phpK0bZ8B, aes-256-gcm
    . encrypting /tmp/php7woXgG: /tmp/phpNmmIpC, aes-256-gcm
    . encrypting /tmp/phpT1EufE: /tmp/phpSM024D, aes-256-gcm
    . encrypting /tmp/phpHcJjWC: /tmp/phptDt6aG, aes-256-gcm
    . encrypting /tmp/phpqHmS4E: /tmp/php28kBpG, aes-256-gcm
    . encrypting /tmp/php4U3cyG: /tmp/phpcrZmbD, aes-256-gcm
    . encrypting /tmp/phpUrtKoD: /tmp/phpJHBmzF, aes-256-gcm
    . encrypting /tmp/phpNsMbDE: /tmp/phpoMv9EF, aes-256-gcm
    . encrypting /tmp/phpC67qnE: /tmp/phpmYyfqF, aes-256-gcm
    . encrypting /tmp/phpCV4TaC: /tmp/phpnzb3uC, aes-256-gcm
    . encrypting /tmp/phpsEe6UC: /tmp/phpJ4YokF, aes-256-gcm
    . encrypting /tmp/phpRYp8cC: /tmp/php4GJk3F, aes-256-gcm
    . encrypting /tmp/phpoWUSuD: /tmp/php6Tgj0D, aes-256-gcm
    . encrypting /tmp/phpy9cKwD: /tmp/phpJhHaKD, aes-256-gcm
    - storing parts in appdata ...............................ok
    * Removing old chunk file data-57d12a73-84ed-417b-9800-dd09016a1318.zip

In PackService.php line 210:
                                                                                                                                                                                    
issue on chunk data-57d12a73-84ed-417b-9800-dd09016a1318 - /appdata_ocnjhhw03bau/backup/20220112111713-full-lQoHZL8oq5FL82h/data/data-57d12a73-84ed-417b-9800-dd09016a1318/data-5  
7d12a73-84ed-417b-9800-dd09016a1318.zip                                                                                                                                            

Any idea on what's the underlying issue or how I could get more information on it?

Start with PackService.php around line 210 and reproduce the failure using the reported backup:point:pack command and restoring point. Trace the failing chunk after its parts are stored and the old chunk file is removed, using the reported chunk ID and path as identifiers. Done means the underlying failure is identified and packing completes or reports a clear actionable error.