Fix Preview Bug In case the file preview is erroneous/empty but the file can be processed and it can be downloaded by URL like https://dms.yourdomain.de/api/file/:FILE_ID/data : Root Cause: unkown. Seems to happen after migration from H2 to PostgreSQL Fixing proposal Remove the _thumb and _web files and let Teedy create new ones by running a (complete) re-processing cd /var/docs/storage ll | grep "" mv _thumb _thumb.bak mv _web _web.bak #or just move all stuff to some sub directory if you plan to re-process the complete file system: mkdir thumb_web_bak mv *_thumb *_web thumb_web_bak/ #restart your instance to let Teedy recognize that changes due to caching sudo systemctl restart jetty9.service Reprocess documents See Teedy API Scripts / database queries for reprocessing of everything.