Your guess is right, Nik. Rebuilding thumbnails is improving the quality of the 3FR raw-file. Now I need to know where these previews are stored as I host all other raw-converter databases on an external SSD. I’d like to do the same with Nitro but so far I haven’t found a database related to Nitro. If Nitro needs the internal disk which is limited and very expensive at Apple, I can’t use it in the future to fill it up with JPG previews.