July 2017 - last edited May 2020
Map Reloading is the issue where when you try to load a lot in your game, all it does is going back to the map instead of actually loading the lot. There's usually also an error code in the form of: <ThreeDigitNumber>:<LongHexNumber1>:<LongHexNumber2>.. More information on these can be found here: Loading a family just reloads the map
This problem isn't as much as a bug but a symptom of a problem that occurs in your game. The game tries to load the household and then hits a problem/corruption and can't load the lot because of that. It then bounces back to the world screen.
EA/Maxis has fixed a lot of causes for this since it first started happening but there's still issues around and causes need to be found. It could be something on the lot or a faulty Sim or object. You can either try troubleshooting yourself or upload your save game so EA/Maxis can take a look at it. They might find a cause and fix it in the next update.
Outdated mods are a major player in this so if you can't pinpoint your error to a specific save game, it's probably a mod.
Also there's no guarantee that it's not coming back after playing a while so make sure to make backups.
Incompatible mods can be one reason for this. If you have it, please remove all your mods and try on a vanilla game to make sure that's not your issue. If it runs fine, without mods, use the 50/50-Method to find out which mod is causing the issue for you. It's also possible it's a conflict among mods or outdated custom content like hair/furniture or clothing.
There's also been several game issues that caused this. Most have been already fixed by EA/Maxis.
Currently active causes
If you ruled out mods, try to isolate the save game it's happening on and check if it's happening on all lots or just certain ones (remember you have to completely shut down the entire game each time you land back on the map).. Check if you have any of the known causes outlined above.
If you need help narrowing down the issue, zip this folder: documents\electronicarts\thesims4\saves and upload to OneDrive or Google Drive. Then create a new thread and post the link there along with as much info as you can give.
If you are uploading your saves folder, please state which game you have issues with and which family doesn't load or what you're doing. Also post which Addons you have.
Instructions how to salvage your house and Sims if the game no longer works
You should still be able to upload to family/house to the gallery (or just save to your library) and put them in a new game (This might not work for the newest problem occurring)
I don't work or have any association with EA. I give advice to the best of my knowledge and cannot be held responsible for any damage done to your computer/game.
Please only contact me via PM when asked to do so.