Internal Server Error after restoring server image

Nextcloud version: 21.0.5
Operating system: Raspberry Pi OS Buster 10
Apache version: 2.4.38
PHP version: 7.3

Issue: I just restored a disk image of my Nextcloud server on Raspberry Pi Buster after an unsuccessful upgrade to Bullseye. Everything else is working, but Nextcloud, it seems.

Is this the first time you’ve seen this error?: Yes.

Steps to replicate it:

  1. Do a full dd image restoration
  2. Run the server
  3. Get ‘Internal Server Error’

The output of your Nextcloud log in Admin > Logging:

N/A because I can't access it by logging in.

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

<?php
$CONFIG = array (
  'instanceid' => 'instantlove',
  'passwordsalt' => 'toomuchsalt',
  'secret' => 'toomanysecrets',
  'trusted_domains' => 
  array (
    0 => 'someurl.com',
    1 => '10.10.10.100',
  ),
  'datadirectory' => '/var/www/nextcloud/data',
  'dbtype' => 'mysql',
  'version' => '21.0.5.1',
  'overwrite.cli.url' => 'https://someurl.com:696969',
  'dbname' => 'nextcloud',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'mysql.utf8mb4' => true,
  'dbuser' => 'oc_someuser',
  'dbpassword' => 'noonewillfigurethisout',
  'installed' => true,
  'memcache.local' => '\\OC\\Memcache\\Redis',
  'memcache.locking' => '\\OC\\Memcache\\Redis',
  'filelocking.enabled' => 'true',
  'redis' => 
  array (
    'host' => '/var/run/redis/redis.sock',
    'port' => 0,
    'timeout' => 0.0,
  ),
  'enable_previews' => true,
  'enabledPreviewProviders' => 
  array (
    0 => 'OC\\Preview\\TXT',
    1 => 'OC\\Preview\\MarkDown',
    2 => 'OC\\Preview\\PDF',
    3 => 'OC\\Preview\\Image',
    4 => 'OC\\Preview\\Photoshop',
    5 => 'OC\\Preview\\TIFF',
    6 => 'OC\\Preview\\SVG',
    7 => 'OC\\Preview\\Font',
    8 => 'OC\\Preview\\MP3',
    9 => 'OC\\Preview\\Movie',
    10 => 'OC\\Preview\\MKV',
    11 => 'OC\\Preview\\MP4',
    12 => 'OC\\Preview\\AVI',
  ),
  'preview_max_x' => 512,
  'preview_max_y' => 512,
  'maintenance' => false,
  'theme' => '',
  'loglevel' => 3,
  'app_install_overwrite' => 
  array (
    0 => 'calendar',
  ),
  'default_phone_region' => 'CA',
  'updater.release.channel' => 'stable',
);

The output of your Apache/nginx/system log in /var/log/____:

[Sat Nov 20 13:42:27.429287 2021] [php7:error] [pid 729] [client 10.10.10.100:696969] PHP Fatal error:  Uncaught Error: Class 'OCA\\DAV\\Connector\\Sabre\\ExceptionLoggerPlugin' not found in /var/www/nextcloud/remote.php:61\nStack trace:\n#0 /var/www/nextcloud/remote.php(169): handleException(Object(RedisException))\n#1 {main}\n  thrown in /var/www/nextcloud/remote.php on line 61

If there’s anything else I need to provide, please let me know. I’d like to get this working again and learn from it asap. Thanks.