wmayer wrote:I don't know if this is still true for Gnome3 but in Gnome2 you have the directory $HOME/.thumbnails with two sub-directories. inside there you have PNG files with a GUID as file name. I think when deleting all the files there you should see the correct thumbnail for exiting fcstd files.
Hey thanks, I just tried this and it solved my problem.
There are actually 3 folders: fail, large and normal. In fail, there was a folder named gnome-thumbnail-factory whith a few hundreds bad PNGs. I deleted them, went back to my folder containing FreeCAD files, and the thumbnails show up again. It seems this folder says to Nautilus not to attempt to rebuild thumbnails for files it failed before.
It looks like this is an old GNOME bug. https://bugs.launchpad.net/nautilus/+bug/305850
Next I'll have to delete the .thumbnailer files I created, to check if they actually are useful.