After about 55 hours of gameplay in Career mode (having established a museum in all five areas), I lost my save file and all of my progress. The game would not recognize my save file, even after I checked if it still existed in the games files. I tried to implement the fixes that you guys have suggested, only to be missing a necessary file (“career.csav.2.bak”), and thus, being unable to fully go through with the instructions. I then booted up a sandbox file, and after roughly 4-5 hours in, I lost the save file mid-game by logging out to the main menu, and finding the save completely missing with a simple red exclamation mark over the top-left corner of the save file page. Before this most recent loss, the "save" icon of the pick-axe mining a rock to uncover a floppy disk was frozen in place instead of disappearing after an auto-save.