The Sims 4 has officially released on the Xbox One and PlayStation 4 today, but it looks like there's something that keeps corrupting player saves. The team behind The Sims 4 on PS4 and Xbox One have taken note of the issue and are currently investigating.
The Sims 4 team member Arvin suggests "saving the game immediately after entering live-mode, and after traveling." Arvin went on to say to "close and restart the game" once the issue is encountered.
A forum goer has offered up a workaround that has worked for some members of the community.
"Instead of saving your game, hit 'Manage Worlds' then go straight to Worlds without saving. Immediately press the menu button and return to the main menu, again without saving. Go back and load the autosave for your character and it SHOULD work."
No update to resolve the issue has been released yet, however, you can check on the status of updates here.