I'm using DraftSight 2018 x64 SP1 and always save drawings with thumbnails. Most are in folders in list view. Some are in folders with large icon view. The preview pane shows the drawing contents in both instances, but the large icon view keeps losing the thumbnail in the folder pane. I manage to get them back by reinstalling software, but after a few weeks they disappear again. No software is installed or uninstalled and no settings are changed. It seems to be on some sort of timer, because of the regularity. Why does this happen and how can I stop it?