Sorry you're running into this issue! Most of the save file or loading errors have been fixed over development but it sounds like you're running into a new one we haven't seen. Would you be able upload your log file for us to look at? It is located at the directory below. Make sure you link a log that was generated after the bug occurred as well.
C:\Users\USER\AppData\LocalLow\Monothetic\Beacon\Player.log