Summary: Another save that won't load. I attached a good one from the same game, however, so maybe you can compare the two (only two turns between them) and figure this out. 

Description: Summary describes it. 

Steps to Reproduce: Try loading AutoSave 4097 (attached to thread), with or without preview 1.0.25.

Reproducibility: 5/5

Expected Behavior: ...

Version: 1.0.25 preview (Steam). I opted into the beta after my save failed to load.

Notes: Experienced a horrendous memory leak while playing the turns after AutoSave 4095. When this leak happens, you can watch the process size grow by almost 1GB per turn, depending on who-knows-what. The leak is rough on performance, too, as the game starts hanging constantly every few seconds, and won't stop until the process is killed and reloaded. Apart from this issue with this game, my system is completely stable. 100% legit software, and everything else I have ever wanted to run on this computer runs without any hassle, memory leaks, or noticeable failures of any sort. I do not pirate, nor will I ever.

I think your memory leak is the key to solving the problem of bad data being written to your saves. I went 300 hours (with some sleep) on Endless Space 2 before encountering a save that wouldn't reload. Before, I used to just curse at the pausing but press forward, since the game remains almost playable while the rampant process growth occurs. I'm less patient now, though, so I began saving and restarting the process after the first signs of the memory leak came back. That was the first time in over 300 hours of play that I ever encountered the save game bug.

Attachments: 

1. AutoSave 4095.zip - Turn 216 of custom game where I'm playing United Empire and arranging a score victory.
2. AutoSave 4097.zip - Turn 218 of same game, not loadable under any available [to me] versions of Endless Space 2. I used whatever your production version is on Steam until the save failed to load today. After that, I opted into the 1.0.25 preview to find my problem unchanged.

Please note that the memory leak (or bizarre process growth) is something I've endured with regularity, almost every time the game runs for longer than 3ish hours in one sitting. I cannot force the leak to occur, though, and thus cannot tell you if 1.0.25 is free of this leaky behavior. I can tell you, however, that 1.0.25 will not load the second save I attached.

edits: meh, I only proofread after hitting post. ;) 

System configuration:

• Windows 10 Pro
• i7 6950X (10 core), 64GB RAM
  • All clock speeds are stock. Nothing, not the RAM, GPU, or CPU are overclocked. I got the chip new for half price and haven't set to clocking it up, just yet. Plus, I'm lazy.
• NVidia GTX 1080 (Asus A8G, just the one)
  • 384.76
• Steam, good Internet service

Please advise if further data is required.