Cannot create file names or dirs containing a "+" sign (plus sign)

Nextcloud version (eg, 12.0.2): 18.0.1
Operating system and version (eg, Ubuntu 17.04): CentOS 8
Apache or nginx version (eg, Apache 2.4.25): 2.4.37
PHP version (eg, 7.1): 7.4.2

The issue you are facing:

Cannot create files or folders containing a “+” sign (“File could not be created”).
Problem came up after upgrading to v17, I think. And switching to 4-Byte support.
Legacy files containing a “+” sign in their file names cannot be synced by the client (“file missing”).
Strange thing: I migrated the installation in a fresh VM from CentOS 7 to 8 and immediately after that I could create files containing a “+” sign. After the client started syncing the show was over again.

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

Steps to replicate it:

  1. Try to create new file containing “+” sign

The output of your Nextcloud log in Admin > Logging:

No respective logging available; seems as if the Javascript / GUI throws the error.

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

$CONFIG = array (
‘passwordsalt’ => ‘secret’,
‘secret’ => ‘secret’,
‘trusted_domains’ =>
array (
0 => ‘cloud.XXXXX.de’,
1 => ‘192.168.10.207’,
2 => ‘*.XXXXX.de’,
),
‘datadirectory’ => ‘/XXXXX/nextcloud/data’,
‘overwrite.cli.url’ => ‘https://cloud.XXXXX.de/’,
‘htaccess.RewriteBase’ => ‘/’,
‘dbtype’ => ‘mysql’,
‘version’ => ‘18.0.1.3’,
‘dbname’ => ‘nextcloud’,
‘dbhost’ => ‘localhost’,
‘dbport’ => ‘’,
‘dbtableprefix’ => ‘oc_’,
‘dbuser’ => ‘nextcloud’,
‘dbpassword’ => ‘secret’,
‘logtimezone’ => ‘UTC’,
‘installed’ => true,
‘default_language’ => ‘de’,
‘default_locale’ => ‘de_DE’,
‘defaultapp’ => ‘files’,
‘knowledgebaseenabled’ => true,
‘ldapIgnoreNamingRules’ => false,
‘ldapProviderFactory’ => ‘\OCA\User_LDAP\LDAPProviderFactory’,
‘mail_from_address’ => ‘Cloudmaster’,
‘mail_smtpmode’ => ‘smtp’,
‘mail_domain’ => ‘XXXXX.de’,
‘mail_smtphost’ => ‘192.168.10.202’,
‘mail_smtpport’ => ‘25’,
‘loglevel’ => 2,
‘logdateformat’ => ‘F d, Y H:i:s’,
‘maintenance’ => false,
‘memcache.local’ => ‘\OC\Memcache\APCu’,
‘memcache.distributed’ => ‘\OC\Memcache\Redis’,
‘memcache.locking’ => ‘\OC\Memcache\Redis’,
‘redis’ =>
array (
‘host’ => ‘localhost’,
‘port’ => 0,
‘dbindex’ => 0,
‘password’ => ‘secret’,
‘timeout’ => 1.5,
),
‘instanceid’ => ‘XXXXX’,
‘mail_sendmailmode’ => ‘smtp’,
‘onlyoffice’ =>
‘onlyoffice’ =>
array (
‘verify_peer_off’ => true,
),
‘mysql.utf8mb4’ => true,
);

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

Nothing concerning this error there