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

 Since the newest updated whenever I try to enter my household I'm stuck in an infinite loading screen. ive removed all mods, uninstalled and reinstalled the game and repaired it multiple times. I'm able to enter other households in the same save as mine though so I dont believe my save is broken. 

I did the second option and it worked! Thank you so so much.

Hi jmmw326​ 

That's the milestone tracker issue. It happens if you remove cc object that had milestones attached to them (like infant playmats which are the most common culprit).

You have two options:

1. Put the cc playmat back into your game
2. Fix the error with a mod: https://www.patreon.com/posts/mod-milestone-81237568 (File 2: CC/Mod Object Fix)

Let me know when you fixed it. I will then merge this thread with the main one.

<?xml version="1.0" ?><root>
<report><version>2</version><sessionid>621e518c17d9980d68ab67c2</sessionid><type>desync</type><sku>ea.maxis.sims4_64.15.pc</sku><createtime>2025-08-24 14:28:59</createtime><buildsignature>Local.Unknown.Unknown.1.117.227.1030-1.200.000.673.Release</buildsignature><categoryid>developmental_milestone_tracker.py:1114</categoryid><desyncid>621e518c17d9980d68ab67c2</desyncid><systemconfig/><screenshot/><desyncdata>Exception raised while processing zone spin up sequence: 'Object not found: 0x31baa98' (KeyError: 'Object not found: 0x31baa98')&#13;&#10;Traceback (most recent call last):&#13;&#10;&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\areaserver.py", line 130, in wrapped&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\areaserver.py", line 126, in finally_wrap&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Core\sims4\utils.py", line 157, in wrapper&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Core\sims4\utils.py", line 175, in wrapper&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\areaserver.py", line 383, in c_api_client_connect&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\zone.py", line 612, in do_zone_spin_up&#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 846, in on_update&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\zone.py", line 1076, in on_all_sims_spawned&#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 274, in start_milestone_tracker&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\developmental_milestones\developmental_milestone_tracker.py", line 731, in _activate_available_milestones&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\developmental_milestones\developmental_milestone_tracker.py", line 565, in activate_milestone&#13;&#10;  File "T:\InGame\Gameplay\Scripts\Server\developmental_milestones\developmental_milestone_tracker.py", line 315, in process_evaluation&#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: 0x31baa98'rtim=0&#13;&#10;Client Session Time: 18.88&#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: 13,535,0,6048&#13; &#10;Modded: False&#13; &#10;SystemInfo: Windows 11 10.0.26100 GPU: NVIDIA GeForce RTX 4060 Laptop GPU nvldumdx.dll 32.0.15.7628, GUID: D7B71E3E-6BA0-11CF-546E-F82B0EC2ED35&#13; &#10;</desyncdata></report>
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Hi jmmw326​ 

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. 

I have had the same save file for around 9 years and after this latest update I can no longer play in it. In this save file, I can enter CAS just fine but when I try to play any of my households I get an Error Code 110:3335857a;10c3bfad. I know this code is for broken mods but I removed all my mods from the game and it still showed up. Then I uninstalled and reinstalled and the error code still showed. I then factory reset by deleting the sims 4 file. Playtesting with a new household and save was fine but when I moved this saves backup back the same error code showed up when I tried to play. I've also tried attempting to load again after the error message and instead of an error message the second time, it just loads forever. This doesn't happen to any of my other saves, just this one. I wonder if it is because it is from 2016/17? I'm not sure how to attach my save file. If it is need tell me and I'll figure it out. I think I posted in bug reports but im not sure where it went or which one is the correct place to post sorry. 

I have had the same save file for around 9 years and after this latest update I can no longer play in it. In this save file, I can enter CAS just fine but when I try to play any of my households I get an Error Code 110:3335857a;10c3bfad. I know this code is for broken mods but I removed all my mods from the game and it still showed up. Then I uninstalled and reinstalled and the error code still showed. I then factory reset by deleting the sims 4 file. Playtesting with a new household and save was fine but when I moved this saves backup back the same error code showed up when I tried to play. I've also tried attempting to load again after the error message and instead of an error message the second time, it just loads forever. This doesn't happen to any of my other saves, just this one. I wonder if it is because it is from 2016/17? I'm not sure how to attach my save file. If it is need tell me and I'll figure it out. Please help. I cannot stand to lose all these years of this family.

Vamperix​  I've moved your post to the master thread for the milestones issue, which your lastexception lists.  Please install the mod linked in the accepted solution.

<?xml version="1.0" ?><root>
<report><version>2</version><sessionid>59d2c23aa171a15f68a8b6ca</sessionid><type>desync</type><sku>ea.maxis.sims4_64.15.pc</sku><createtime>2025-08-22 14:29:30</createtime><buildsignature>Local.Unknown.Unknown.1.117.227.1030-1.200.000.673.Release</buildsignature><categoryid>developmental_milestone_tracker.py:1114</categoryid><desyncid>59d2c23aa171a15f68a8b6ca</desyncid><systemconfig/><screenshot/><desyncdata>Exception raised while processing zone spin up sequence: 'Object not found: 0x2a1d81e6' (KeyError: 'Object not found: 0x2a1d81e6')&#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\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: 0x2a1d81e6'rtim=0&#13;&#10;Client Session Time: 14.59&#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: 13,535,0,6048&#13; &#10;Modded: False&#13; &#10;SystemInfo: Windows 11 10.0.26100 GPU: NVIDIA GeForce RTX 3080  32.0.15.8097, GUID: BDA88772-40F6-11F0-A2AB-806E6F6E6963&#13; &#10;</desyncdata></report>
</root>

last exception file from my game after the newest update tried repairing the game and deleting thumbcache, no mods or cc vanilla game but still having the same issue, back to the sims 3 i go :/

msnijder30​  From what I've heard, you should be able to remove the milestone fix mod once you save your progress with it present.

The reason for this error, the one that the mod fixes, is that when a sim achieves a milestone, some data references what object they used to do so, for example a playmat.  If the object is custom content, and you remove the cc, you won't be able to load that household.  So you could also just put back your cc objects to fix the problem.

And to be clear, it's not that you need to keep the item on the lot.  The point is that the game has to load the object in general, like in the Build/Buy catalog.