If your Space Engineers server starts, sits for a few seconds, then drops straight back to stopped (sometimes on a loop), open the Log Viewer or Web Console and you'll almost always find the same thing near the bottom:
ProtoBuf.ProtoException: No parameterless constructor found for VRage.ObjectBuilders.MyObjectBuilder_Base
Error during loading session: Sector could not be loaded
Exiting..
We get this one in tickets every so often. It looks scary, but it's usually recoverable, and in most cases you don't lose your world. Here is what it actually means and how to get back up.
What the error is telling you
A Space Engineers save is really two parts. There's the settings side (Sandbox.sbc, which holds the world name, mod list, GPS points and faction data), and there's the sector (the large SANDBOX_0_0_0_ file that holds the actual grids, blocks and voxels).
The useful detail buried in that log is that the settings load fine. You'll see your world name and the in-game date print in the lines just before it dies. It's the sector that won't read. So your configuration is healthy, it's the build data that the server can't make sense of. That narrows things down a lot, and it's why a clean backup almost always rescues you.
Why it happens
Three causes cover nearly all of these:
- An interrupted save. If the server was killed in the middle of an auto-save (a crash, an out-of-memory, or a hard stop that landed right on the auto-save tick), the sector file ends up half-written. Space Engineers auto-saves every few minutes by default, so the window for this is real.
- A version gap. If the save was made on a newer game build than the server is currently running, or the game updated underneath an older save, the sector format won't line up and you get this exact error.
- A missing mod. If the world was built with a Workshop mod that has since dropped out of the world's mod list (or vanished from the Workshop), the blocks that mod added have nothing to load into.
First thing: stop the restart loop
Before you touch a single file, hit Stop on the server page in the LOW.MS Control Panel and leave it stopped while you work. Space Engineers servers are set to restart after a crash, so if you just leave it running it will keep throwing itself at the same dead save every few seconds. That's noise in the log and it makes it harder to see what you're doing. Stop it first, then work calmly.
The good news: you almost certainly have a backup
This is the fix in the large majority of cases, and it keeps your world.
Cloud Restore is the easy button. Open your Space Engineers service in control.low.ms and use Cloud Restore. Pick a restore point from before the server started failing and let it roll back. Our cloud backups run on a schedule, so there's usually a clean copy from earlier that day or the day before. If you're not sure exactly when it broke, the Log Viewer timestamps tell you when the first "Sector could not be loaded" showed up, which is your cutoff.
If Cloud Restore doesn't have quite the point you want, Space Engineers also keeps its own rolling backups inside the save itself. In File Manager, open Saves/<YourWorld>/Backup/ and you'll see timestamped copies from recent auto-saves (you'll spot SANDBOX_0_0_0_.sbsB5 and similar in there). Restore the most recent backup that loads, even if it costs you a few minutes of progress. The newest one that opens cleanly is the one you want.
Backup Manager is a third place to pull a known-good copy from, holding the local backup files the panel keeps if Cloud Restore and the in-world Backup folder both come up short.
Whatever route you take, grab a fresh Cloud Backup of the current broken state first if you can. It costs nothing and it means you can't accidentally make things worse while you're poking around.
If it broke the moment the game updated
If the failure started right after a patch, you're probably looking at the version gap rather than a corrupt file. Run Steam Update from the panel so the server is on the current build, then start it. A server running older binaries than the save will refuse to load the newer format, and getting it current usually clears it straight away. If it went the other way and the server updated past a save you care about, restore that save from a backup taken on the matching build instead.
If you would rather just start fresh
Say the old world is a write-off and you don't care, you simply want a clean slate. There's one thing worth knowing here, because it catches almost everyone out:
A Space Engineers server will not spin up a brand-new world on its own just because the old one is gone. It loads the world it is pointed at. If that world is broken and there's nothing valid to fall back to, it just exits, which is exactly the loop you're stuck in. Deleting the save does not trigger a fresh one to generate.
Two specific traps that waste people an afternoon:
- Renaming the broken save folder inside
Saves/does not stop it loading. The server will happily pick up whatever world is sitting inSaves/, whatever it happens to be called. If you want it gone, move it out ofSaves/entirely (or download it and delete it). Don't just rename it in place. - An empty
Saves/folder doesn't get you there either, for the same reason. The server still needs a world handed to it.
The reliable way to get a fresh world is to make one and give it to the server. The easiest path by far is to create a new world in single-player Space Engineers exactly how you want it (settings, scenario, the lot), then upload it. I've written that up step by step here: Space Engineers Save Location & How to Upload Your World. Once it's sitting in Saves/ and the server is pointed at it, you're away.
If you'd rather not fiddle with any of that, open a support ticket and ask us to set up a clean world for you. It's a quick job on our side and we're happy to do it.
A few things not to do
- Don't keep hammering Start hoping it eventually catches. It won't. The sector is the sector, and every attempt reads the same bytes.
- Don't upload or edit files while the server is running. Space Engineers writes to the live world on a timer, and dropping files on top of a running session is one of the classic ways saves get corrupted in the first place.
- Don't delete your only copy of a world you care about before you've confirmed a backup actually loads. Move it aside, prove the replacement boots, then clean up.
If you've worked through all of that and it still won't load, send us a ticket with the service name and roughly when it started failing. We can pull the logs and the backup history from our side and get you sorted.