Well, I wasn't ready to deal with something that wasn't completely clear to me, so I resorted to using a neural network. The neural network informed me that the problem was the loss of data between saves. The next paragraph is the text from the neural network for you.
The Sims 4 save files become corrupted — missing save thumbnails and world/lot data
Platform: PC Windows
Game:The Sims 4
Issue:Save files become severely corrupted during normal gameplay.
1. Description of the problem
I have been experiencing recurring save file corruption in The Sims 4.
At seemingly random times, the thumbnail/cover image of a save slot disappears. This can happen while I am playing or even when I first launch the game, before loading the affected save.
When I load a save with a missing thumbnail, I may find that large amounts of world and lot data are missing:
- Worlds may revert to their default buildings.
- Lot types may remain customized, but the actual buildings and lot data may be missing.
- Some lots may disappear when I try to enter them.
- The active household's current lot may sometimes remain intact, while other lots are affected.
This is not limited to one particular save slot.
2. Reproducibility
The issue is intermittent and difficult to reproduce consistently.
It can occur after normal gameplay and saving. I usually save while playing at my active household's home lot.
Both **Save** and **Save As** can be affected. The problem does not appear to depend on which option I use.
I have also experienced the issue after switching to a different save slot. Creating a new slot does not appear to prevent the corruption permanently.
3. Troubleshooting already performed
I have tried the following:
- Completely deleted the The Sims 4 folder from Documents and allowed the game to generate a fresh folder.
- Tested the game with mods and custom content removed.
- Disabled OneDrive a long time ago; the Sims 4 folder is not synced through OneDrive.
- Disabled in-game autosave.
Despite these steps, the issue has continued.
4. Technical observations
I examined one severely corrupted save file alongside a working save file using DBPF structural analysis.
The working save contained approximately **1,520 indexed resources**, including **417 Zone Object Data resources**.
The corrupted save contained only **2 indexed resources**:
- Save Game Data
- Zone Object Data for the active household's lot
The other 416 Zone Object Data resources and numerous other resource types were missing from the corrupted file's index. The corrupted file also contained two identical copies of Save Game Data and two small DBPF indexes, both containing only those same two resources. This suggests that the problem may involve the save-writing process or the handling of save data, rather than simply a missing thumbnail. I understand that this analysis does not establish the exact cause, but I hope it may help with investigation.
5. What I would like to know
- Is this a known issue involving DBPF save file writing or resource indexing?
- Could a race condition, interrupted write operation, temporary/scratch file handling, or another save-system issue cause large portions of a save file to disappear?
- Are there any additional logs or diagnostic files I should provide to help identify the cause?
This issue is particularly frustrating because it can destroy many hours of gameplay without warning. I would really appreciate any help investigating it. I am willing to provide current affected and working save files for comparison.
