Under the preview forums Microsoft has alerted Australia and New Zealand players to the fact that the current 1610 preview build has a save game corruption bug in Forza Horizon 3. This will affect Ultimate Edition users.
Around 4am Friday morning EST (Australia) a new 1610 update should come out for preview program members which should fix the issue.
It you were looking at playing the game just after midnight tonight it may be better to wait until after the new 1610 preview build is released first otherwise you risk losing your save game data.
The Late Night Session 
Good news is most people’s issues should be fixed by now and the game runs beautifully. 🙂
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