It's a total shame that EA games cannot chime in and suggest solutions based on their own perspective.
I think I found the best solution.
1. Load up the latest save. Grin and bear the reduction of progress.
2. Switch to build the mode and change a moderate amount of things that you can easily remember.
3. Attempt to save. If the error code does not reappear, Play the game for 15 minutes and reattempt steps 1. Through 3.
4. If the error code appears, remember your last changes to your lot, and save and manage worlds.
5. Reconnect with your main household and reduce the amount of minutes in step number three from 15 minutes down to 10 minutes.
6. If the error code persists, the load on the lot might be too high, or you might need to just save the lot to the library and paste it somewhere else/ repast it to the same lot in a previous save.
7. Tread carefully through steps 1 through 3.