The ZeroDay bug is a problem where your saved world is reset by itself after a server update or restart.
The fix is quite simple
- Shut down the server
- Click on FileManager
- Click through the folder structure to ShooterGame/Saved/SavedArks
- Find the saved map files "Mapname.ark" and "Mapname_date_time.ark"
- Note that the files will have very different sizes, the ones that are corrupted are smaller in size
- The file that ARK reads as active is always the one without the date
- Rename this file
- Then find the file with the most recent date that still has the correct (larger) size
- Rename this file to the original file name without the date, i.e. "MapName.ark"
- Start the server and double check that the server is restored
