Your Sims Saves Might Finally Stop Breaking After December’s Update

The Sims team has been investigating one of the biggest bugs plaguing the game since forever — corrupted Save Files! The bad news is there’s no single cause for save corruption, but they’re working on untangling the issue piece by piece, with more updates coming in December 2025.

Here’s the full message from the EA forums:

Welcome to our November update into save file investigations. Over the past few months, our team has been testing, analyzing, and dissecting every lead – from missing lots to infinite loading loops – to understand what’s really happening under the hood. Thanks to our new Python-based tool and a growing database of player-submitted saves, we’ve identified several consistent patterns that point to the root causes of these problems.

Here’s a high-level overview of where we’re at and where we’re headed, with more technical details below.

1. Fixed a cause of infinite loading on November 4th. Our team was able to identify and reproduce an issue that was causing infinite loading when converting Penthouses or Dorms into Residential Rentals. This issue was discovered internally, not linked to any previously ongoing investigations, and began with Adventure Awaits. A fix was shipped out alongside the community voted issues in the November 4th Base Game update.

2. Thanks to the community providing their affected saves, we’ve also been able to resolve the underlying causes for Error code: 109:4fe45107, Error code: 109:d7e16575, and Error code: 123:b378c837 in the saves that they were originally occurring in. You can expect to see these fixes in our upcoming Base Game update in December. This does not mean that these error codes will no longer occur, but we can confirm that we’ve resolved the issue that was triggering the error in the provided saves. If you do run into these error codes again, please let us know on EA Forums and provide your save file to the team as we work to eliminate other causes.

3. We’re also exploring what we call a “Protobuf Overflow” – a case where save or Lot data grows so large it exceeds its storage limits, leading to missing or corrupted Lots. The good news is that our Memory Boost Feature seems to reduce this risk, and we’re continuing to test this theory using intentionally overstuffed save files.

We’re also tackling Error 801, where multiple processes compete during load and can crash the game, and we’ve begun the process of moving scratch files from the Documents folder to AppData to prevent conflicts with cloud backups. On top of that, we’re investigating event overlaps, cheat-heavy or modded Lots, lingering mod data, and even cases where venue data carries into new saves.

The further we investigate these issues, the more we’re certain that save corruption has no single underlying cause, there is no “patient zero”. More accurately, save corruption is akin to “18 bugs in a trench coat” that we continue to curtail as we progress.

– The Sims Team

Our Current Investigations:

Protobufs – Missing Lot Data

Our investigations suggest that missing Lot data may be caused by a “Protobuf Overflow.” Protobufs are the data files that store information about your saves – but they have a size limit. When a save or Lot grows too large (for example, due to extremely packed builds or complex saves), it could exceed that limit and cause corruption.

We’re currently testing this theory using an intentionally overstuffed save file and have found that the Memory Boost feature has the ability to to help reduce the likelihood of overflow, therefore preventing this issue from occurring on some hardware configurations. Our investigations are ongoing in this area, but this discovery gives us a solid direction for potential fixes to issues related to corrupted Lots and disappearing houses in saves with lots of rental units.

We’ve done some testing on saves where lots appear missing and found that sometimes loading that save with the Memory Boost feature enabled can cause them to appear again. Our investigations are ongoing in this area, but given that both hardware and software are involved, it means we need more time to investigate this thoroughly so that we can come up with a proper solution. However, we do feel we have a solid direction and you can help us speed this up by filling out the survey linked below.

Error 801 and Scratch File Investigations

We’re actively working to better understand the underlying causes of Error 801, which can cause the game to crash before loading. Our current testing suggests that multiple processes might be competing to finish at once, creating inconsistent results.

Although we haven’t confirmed scratch file deletion as a direct cause of corruption, we’re taking extra precautions. To prevent conflicts with cloud backup services, scratch files are being moved from the Documents folder to AppData in a future update. This change is currently in internal review to ensure stability while we collaborate with other internal teams on scratch files and their interactions with The Sims 4.

Other Areas of Focus:

Overstuffed and Cheated Lots:

We’re testing how Move Objects and heavily decorated or modded Lots from the Gallery behave when downloaded into new games. Our theory is that the game struggles to resolve certain cheat-related placements when those cheats aren’t enabled – possibly causing corruption in large, complex builds.

Potential Corruption Via Gallery Downloads:

In some cases, mod data has persisted inside a save file even after the mod was removed. This can happen with mods that add excessive Lot traits or custom scripts. We’re looking into whether this leftover data can also transfer through Gallery uploads, creating issues for players who don’t have those mods installed.

Venue Data Carrying Across Saves:

We found that in certain cases, data from one save can carry into a newly created save within the same session, creating a broken save right from the start. This behavior began in Lovestruck and isn’t linked to older reports of corruption, but it helps us understand how different systems can unintentionally interact.

Our Next Steps:

Missing Lot Data Survey

We’re looking to gather more information from anyone who’s experienced issues around missing Lot data, and we’ve set up a quick survey to gather information like Memory Boost interactions with previously broken saves, DXdiags, and any mods you have installed, as we think this may be critical to our ongoing investigation into these issues.

We continue to investigate the issues discussed in this article, and look forward to gathering even more useful information from you via the survey linked above.

Once again, your save data continue to be vital to this work – every file you share helps us identify new patterns and move closer to long-term fixes. Thank you for your patience and passion as we work to keep your Sims’ worlds safe, stable, and corruption-free.

Thank you for reading, we’ll see you back here for our next monthly update in December.

Source: EA Forums