Microsoft has revealed that there is a Forza Horizon 3 save issue that may affect users who purchase the Ultimate Edition and begin playing tomorrow. Users who are on the latest preview update (1610) will experience an issue with their save data for Forza Horizon 3.
“This issue occurs when reaching a certain threshold of game save data and is impacted saving career progress, saving screenshots, and importing designs from previous Forza titles. Please be aware that when saving career progress this issue will not indicate an error is present, however, upon restarting the game saved progress may be lost.”
There is an update that will also release sometime tomorrow that will fix this issue, but keep in mind that if you start playing before downloading and installing this update, it’s incredibly likely that your Forza Horizon 3 save will be deleted at some point.