Occ preview:pre-generate // recreating existing files?

Hi there,

if i run sudo -u www-data php /var/www/nextcloud/occ preview:pre-generate the command is running about 2 hours. In my opinion that should be fine for about 6700 pictures and the first run.
If it finished to generate the previews and i run again the same command, it takes again about 2 hours. But as i understood it, the command pre-generate only should generate previews from new or changed pictures. So the second run of this command should be finished in a few minutes if there is no new picture. What could be wrong in my case?

Is there a way how i can check what the command is doing? To see if it creates all files new or is doing some other stuff?

NC Server: 13.0.4 with Preview Generator 1.0.9

Thank you and best regards,

Did you try: sudo -u www-data php /var/www/nextcloud/occ -vvv preview:pre-generate

-vvv should give more information.