Here is a great reference for using Nextcloud’s command options. Some of these command line switches are very handy as you can’t always do these tasks from the GUI.
Cleanup Nextclouds filecache:
sudo -u www-data php occ files:cleanup
Re-Scan your Nextcloud data:
sudo -u www-data php occ files:scan --all -v
More info and the full listing at:
https://www.c-rieger.de/using-nextclouds-command-line