Nextcloud "file is locked" (423 Locked): fix

Technically yes (filelocking.enabled set to false), but you risk corrupted files on concurrent access. Use Redis instead.

daniele@mikweb: ~/errors — less nextcloud-file-is-locked-423.md

What the message looks like

OCP\Lock\LockedException: "files/9a3c1e7d/Dokumente/Bericht.docx" is locked, existing lock on file: exclusive

File locking uses the database instead of Redis, and locks stay behind after aborts.
An aborted upload or desktop client sync; the PHP process was killed by a timeout.
The file is still open in Collabora or OnlyOffice.
Background jobs do not run (no system cron), so expired locks are not cleaned up.

Which locking backend is configured?
sudo -u www-data php /var/www/nextcloud/occ config:system:get memcache.locking
Check that Redis is reachable
redis-cli ping
Count locks in the database (with DB locking)
mysql -u nextcloud -p nextcloud -e 'SELECT COUNT(*) FROM oc_file_locks WHERE `lock` <> 0;'
Check the background job mode
sudo -u www-data php /var/www/nextcloud/occ config:app:get core backgroundjobs_mode

Use Redis for locking: 'memcache.locking' => '\OC\Memcache\Redis' in config.php.
Switch background jobs to system cron: */5 * * * * php -f /var/www/nextcloud/cron.php in www-data's crontab.
Clear stale DB locks: maintenance mode on, DELETE FROM oc_file_locks WHERE 1;, maintenance mode off.
With Redis, locks expire via TTL; only flush the Redis database in an emergency, and only if Nextcloud is its sole user.
If needed, run occ files:scan --path="user/files/folder" for the affected path afterwards.

Technically yes (filelocking.enabled set to false), but you risk corrupted files on concurrent access. Use Redis instead.

Usually large files plus short PHP timeouts: the upload aborts and the lock stays. Raise the timeouts and use Redis locking.

daniele@mikweb: ~/tools — ls

daniele@mikweb: ~/errors — ls