15 days ago - AndrewT - Direct link
Very hard to say, really. FYI it is not a known problem with this game.

Any mods used in this game?

Does the same happen if you do local saves instead of cloud?  
15 days ago - AndrewT - Direct link
Sorry, I'm a little confused now. You can't make cloud saves at all yet you say they show as broken saves?

In any case let's try a clean reinstall of Steam and game:

- move any valued save games elsewhere, and user_empire_designs.txt from /Documents/Paradox Interactive/Stellaris/ if you have made any custom empires or races.
- "uninstall" in Steam-Stellaris
- exit the Steam app entirely
- manually delete both the Steam/SteamApps/common/Stellaris AND Documents/Paradox Interactive/Stellaris folders
In particular you need to make sure there are no files or folders left under either the Steam Stellaris or Documents Stellaris locations, before installing again.

- delete everything in the Steam folder EXCEPT steam.exe and the SteamApps folder
- run steam.exe to rebuild all that

- re-install game in Steam, run a Steam Verify when done.
- add stellaris.exe AND steam.exe to the exceptions list of your antivirus app; ESPECIALLY if you have Windows Defender, add it to the Ransomware "Apps Allowed Through" list.
- start the game with no mods active and test

Good luck!  
15 days ago - AndrewT - Direct link
Has the game always been like this for you? Or it was okay up to some point?

In your Steam settings, is Steam Cloud Sync enabled?  
14 days ago - AndrewT - Direct link
Then I don't understand why what we did didn't fix it

Crusader Kings 2 is free to play on Steam now, and uses the same save system. Can you see if that game will save to cloud okay please?

Oh, and check your Steam Cloud here:
store.steampowered.com

Sign In

store.steampowered.com store.steampowered.com Does that work? Is it perhaps full?  
14 days ago - AndrewT - Direct link
Steam writes cloud saves to a local folder .../Steam/userdata/YourSteamID#/281990/Remote/save games/ . Are the cloud save files physically there?

If so, right click on this game in your Steam Library, General. Is "keep game saves in the Steam cloud" ticked?  
13 days ago - AndrewT - Direct link
Can you not delete them in the game Load interface?