STEPS TO REPRODUCE 1. Attach a USB drive. 2. Add a folder on the drive as an external collection. 3. Let it generate the Thumbnails. 4. Remove the USB drive. OBSERVED RESULT All the thumbnails disappear. EXPECTED RESULT The thumbnails should remain. This is the behavior on 8.2.0 and is expected. When the drive is plugged back it, the thumbnails slowly return which is not ideal. This can also be replicated without unplugging the drive and just restarting digiKam.
I can't reproduce the problem here on Windows. It can occur if the external removable media have the same partition UUID. This occurs due to production reasons with new hard drives, the manufacturers clone an image during production. Therefore, when using external hard drives with digiKam, they should always be formatted first so that a unique partition UUID is created. In the future we will only use one file UUID in the collections, this is already the case with digiKam-8.2.0, but there is still a fallback to the previous methods. Try to reproduce the problem and create a DebugView log. To do this, use an external hard drive with only a few images. https://www.digikam.org/contribute/ Maik
I downloaded a new build (latest) of 8.3.0, dated 2024-01-11 and this problem is no longer present. A build I downloaded earlier this year had that problem even without me formatting the drive first. I just continued from my 8.2.0 database. Thanks Maik, I'm closing this ticket for now