I have read that some players are having issues with SV2020 saves are crashing their games. I am really sorry about that!! It happened to me as well, when I first tried the saves.
How I fixed it is I made sure I had Ella's fixed Sunset Valley.World file downloaded. Deleted my game cache files and then installed the world file.
We've mentioned it's required because SV2020 was built on Ella's fixed world file and works best with it installed.
You can download EllaCharmed’s Fixed World file -
click here to save the file.
Unzip the file (Right-click file and select Extract All).
Click image to see larger view.

-- Before installing the fixed file, rename your original Sunset Valley.world file. I renamed it Sunset Valley.world-Original. That way I still have access to the original file.
Install path may be different then the path shown in image.
Click image to see larger view.

Copy and paste the Sunset Valley.world file into where you installed the Sims 3 game. Usually located in:
<<Install Drive:>> C:\Program Files (x86)\Origin Games\The Sims 3\GameData\Shared\NonPackaged\Worlds
** The install path may be different depending on where you installed Sims 3.Delete the Game Cache Files. - This is best to do whenever you are installing new worlds to play.
From inside this folder \Documents\Electronic Arts\The Sims 3, you can delete the game cache to help the game run smoother:
– CasPartCache.package - CAS parts that appear in Create-A-Sim
– compositorCache.package - New objects that would appear in Buy/Build mode
– scriptCache.package - Mods or Hacks
– simCompositorCache.package - New Sims, default skins
– Sims3LauncherLogFile.log - Uploading/Downloading info in regards to the Exchange
– Sims3Logs.xml - Log Files about your computer and errors that might occur.
– socialCache.package - Simport-related and other social data, if you use the wall to integrate with your MyPage on thesims3.com site
If the above hasn't helped, please read the articles linked below for more tips.
Tips for General Crashing Issues
https://www.carls-sims-4-guide.com/forum/index.php?topic=20732.msg425173#msg425173The Sims 3 | Performance & Bug Fix Guide 2021
https://steamcommunity.com/sharedfiles/filedetails/?id=1131162350