Nextcloud and a supporter account / view?

With redis a file locking cache, such errors should not appear: File is locked - how to unlock

In general, even if there is a locking, it should be removed after some time. If it isn’t it could indicate that your cronjobs are not properly configured (the admin page should show you when the cron jobs were run for the last time, it should be less than 15min) or a client is blocking files all the time.