When the server shuts down, it spits out hundreds of the following errors. "Das Medium ist schreibgeschützt" translates to "The medium / file is read-only".

2020-08-18 08:50:16.979|Main Thread>Session>Backup> Error: There were errors while backing up the save. Deleting corrupted backup data.
2020-08-18 08:50:16.979|Worker Background 0> Error: While serializing temporary file 000000000006D7B8: Das Medium ist schreibgeschützt.
2020-08-18 08:50:16.979|Main Thread>Session>Backup> Error: Can't even delete corrupted backups, what is this world coming to?!

Then, these errors and exception occur:

2020-08-18 08:50:17.090|Main Thread>Session>Saving> Error: While saving current session, restoring last backup.
2020-08-18 08:50:17.090|Main Thread>Session>Saving> Error: While restoring session from backup after save failure: This session contains no backups.
   at Sandbox.Game.World.MySessionBackup.RestoreLatest(String sessionPath, IEnumerable`1 ignoredPaths)
   at Sandbox.Game.World.MySandboxSessionDelta.OnSaved(ExceptionCollector& ex, String destPath)
   at Sandbox.Game.World.MySessionBackup.RestoreLatest(String sessionPath, IEnumerable`1 ignoredPaths)
   at Sandbox.Game.World.MySandboxSessionDelta.OnSaved(ExceptionCollector& ex, String destPath)
2020-08-18 08:50:17.093|Main Thread> Persisting the current session has failed:
2020-08-18 08:50:17.093|Main Thread>     Error: Processing file C:\ProgramData\MedievalEngineersDedicated\ME-Server-1\Saves\Land-of-Endurance\WorldChunks\E5\8_7_-16_3.chunk: Das Medium ist schreibgeschützt.

2020-08-18 08:50:17.093|Main Thread>     Error: Processing file C:\ProgramData\MedievalEngineersDedicated\ME-Server-1\Saves\Land-of-Endurance\world.index: Das Medium ist schreibgeschützt.

At some point, the process just dies and the logging stops. The next time the server boots, 50% or more of the grids are missing.