[CC and Milestones, error code 110-578ef827] Stuck On Loading Screen Sims 4

LIFE SAVER! Thank you

Thank you so much, for trying to help me! 🙂 Sadly his Mod didn't work, because now my game isn't even loading the main menu. (I've downloaded his newest version 3.0) This is the wildest overall bug I have yet experienced. And I never had a broken beyond repair game. I can now only pray that EA will address and fix it 😑

GentleNik​ 

still with only the milestone fix ?

Could be this issue: Frozen game/menu after ad | EA Forums - 12008756 

If not, best if you create a new thread in gameplay for that.

Hi Saabythesimmer​ 

I merged your post with the main thread. That's the developmental_milestones issue. 

Please see first post for solution and cause.

Thanks, I put the milestone mod into my folder, but now I have a new problem. Loading into the main menu does not always work, and if it does, I get a dim screen over the main menu and can't click anything. I wasn't even able to close my game with alt+f4 or make use of the task manager.

Done. All exceptions cleared and this was the one that came up after trying to load the save:

<?xml version="1.0" ?><root>
<report><version>2</version><sessionid>48553b42dc3d60e468c1d656</sessionid><type>desync</type><sku>ea.maxis.sims4_64.15.pc</sku><createtime>2025-09-10 20:54:05</createtime><buildsignature>Local.Unknown.Unknown.1.117.244.1020-1.300.000.220.Release</buildsignature><categoryid>developmental_milestone_tracker.py:1114</categoryid><desyncid>48553b42dc3d60e468c1d656</desyncid><systemconfig/><screenshot/><desyncdata>Exception raised while processing zone spin up sequence: 'Object not found: 0xcdf3a7b7' (KeyError: 'Object not found: 0xcdf3a7b7')&#13;&#10;Traceback (most recent call last):&#13;&#10;&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Core\sims4\utils.py", line 179, in wrapper&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\areaserver.py", line 222, in c_api_server_tick&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\sims\masked\v185b\injector.py", line 26, in _wrapped_function&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\sims\masked\v185b\zone_tick.py", line 83, in _turbolib_zone_game_update&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\zone.py", line 512, in update&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\zone_spin_up_service.py", line 1757, in update&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\zone_spin_up_service.py", line 1389, in on_update&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\zone.py", line 741, in on_hit_their_marks&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\zone.py", line 1142, in _set_zone_state&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Core\sims4\callback_utils.py", line 158, in __call__&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\developmental_milestones\developmental_milestone_tracker.py", line 1206, in send_all_milestones_update_to_client&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\developmental_milestones\developmental_milestone_tracker.py", line 1114, in _get_milestone_update_msg&#13;&#10;KeyError: 'Object not found: 0xcdf3a7b7'rtim=0&#13;&#10;Client Session Time: 41.60&#13; &#10;Num Save Errors: 0&#13; &#10;Num Load Errors: 0&#13; &#10;Current Game State: 0x96d01090&#13; &#10;LoadingScreenActiveFlag: 1&#13; &#10;Origin Version: 13,539,0,6052&#13; &#10;Modded: True&#13; &#10;SystemInfo: Windows 11 10.0.26100 GPU: AMD Radeon (TM) Graphics  31.0.21912.4002, GUID: A4384425-BA82-11EF-8250-806E6F6E6963&#13; &#10;</desyncdata></report>
</root>

GentleNik​ 

I merged your post with the main thread on this error. Please refer to the first post for a solution.

Saabythesimmer​ 

Do you have any LastException files in Documents\Electronic Arts\The Sims 4 ?

- Delete the ones you have
- Trigger the error again
- Check if new ones are created
- If that is the case, please copy/paste the content here. You can open the file with any text editor.

Deleting the file won't fix your issue. Posting the info is meant for troubleshooting. 

With one of my save files I  cannot load into one particular household, It started after the last big update. It's the main save file i play so i have a lot of hours in this save. I  have tried removing and disabling all mods and CC and i have had the same issue, cleared my cache folder, repaired the game multiple times and it's still happening. I can load into other households in the save, i have even tried moving the household onto an empty lot and it's still just loading and playing the game sound so i can hear my sims but cannot play with them as it's still stuck on the loading screen.

I have tried the below but was not able to get to step 3, i cannot force the save option to load up whilst  loading the family with the issue.

1. Load another family
2. Load the family that has the issue
3. Save the game
4. Close the game (completely)
5. Start game
6. Resume save

Any help would be greatly appreciated. 

So I've tried everything for hours. Even followed the crintint Forum for troubleshooting this situation. I keep getting thrown into the World Manager selection screen when wanting to load my family. This only happened after installing the new update. I got an endless Last Exception file, which I've tried to figure out with ChatGPT together. I've updated every mod I can think of. I took them out, but then I get an infinite loading screen. The only thing I could do so far, is start a new vanilla game with renaming the Sims 4 folder into Sims 4_old.

So my own modded game, starting it up vanilla had just one Last Exception (shortened):

Server\developmental_milestones\developmental_milestone_tracker.py

-This is part of the vanilla game system that tracks infant/toddler/child/adult life milestones.

-No external creator is responsible for it — only Maxis/EA.

developmental_milestone_tracker.py", line 1114
KeyError: 'Object not found: 0x27a4b72'

-A Sim in your save is linked to a milestone object that got deleted or corrupted.

Could be from: -An infant/toddler aging up while holding a milestone link. -A household or Sim moved out with milestone data attached. -A rare EA-side bug where the milestone tracker references an invalid object ID