Unfortunately your save file was probably corrupted.
** DON'T ** delete and reinstall the game unless someone from our Support staff specifically asks you to do so. Deleting could destroy any good backups that may still be on the device/computer.
Instead, please update the game (without uninstalling it) to version 2.2.0 or higher if you haven't already done so. Then launch the game and see if the save slot looks normal again. Version 2.2.0 is programmed to identify corrupt saves and, if your save happens to be corrupt, look through all of the backups for an uncorrupt save.
- At the time I write this, version 2.2.0 is only available for Windows computers. It will be coming out soon for the other platforms. Please be patient; we don't run the certification processes, so complaining to us won't make things go faster.