Share link gives file not found for one user

Nextcloud version (eg, 12.0.2): 16.0.2
Operating system and version (eg, Ubuntu 17.04): Debian 4.9.65-3+deb9u1
Apache or nginx version (eg, Apache 2.4.25): Apache/2.4.38 (Debian)
PHP version (eg, 7.1): PHP 7.3.9-1~deb10u1

The issue you are facing:
When one of my users shares a file (in a group folder) using Share Link (with none of the checkboxes checked), following the link gives

File not found
The document could not be found on the server. Maybe the share was deleted or has expired?

Other users who share the same file have no problem.

I have compared the 2 share records in the database, and they are the same (except for the uids, the stime and the token).

Is this the first time you’ve seen this error? (Y/N): Y

The output of your Nextcloud log in Admin > Logging:

There is no log output when accessing either the good or the bad link.

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

$CONFIG = array (
  'passwordsalt' => '(removed)',
  'secret' => '(removed)',
  'trusted_domains' => 
  array (
    0 => 'localhost',
    1 => '(removed)',
  'datadirectory' => '/home/base/ncdata',
  'dbtype' => 'mysql',
  'version' => '',
  'overwrite.cli.url' => 'http://localhost',
  'dbname' => 'nextcloud',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'dbuser' => 'nextcloud',
  'dbpassword' => '(removed)',
  'installed' => true,
  'instanceid' => 'oco7zw7q011j',
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'mail_from_address' => 'cloud',
  'mail_smtpmode' => 'smtp',
  'mail_sendmailmode' => 'smtp',
  'mail_domain' => '(removed)',
  'mail_smtphost' => '',
  'mail_smtpport' => '25',
  'maintenance' => false,
  'default_locale' => 'en-GB',
  'default_language' => 'en-GB',
  'updater.secret' => '(removed)',

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

(my ip) - - [20/Dec/2019:16:50:14 +0000] "GET /index.php/s/9Zj6kW2T5FK33Mk HTTP/1.1" 404 17339 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/79.0.3945.88 Safari/537.36"