UserDefaults reset / erased after iOS 10.3 update

Question

In my SpriteKit game, I use UserDefaults to maintain high scores, etc. It works well, everything works smoothly.

however - I just upgraded some devices to iOS 10.3 (release, not beta), and I noticed that previously saved data is erased ...

new data is saved - for example, a new high score is recorded, so userDefaults are still installed after they are created .. but I would not expect 10.3 to erase the old data?

I assume this is due to the new APFS?

I have not tested this in other applications yet - has anyone else seen this problem? any idea how to prevent this from happening again?

thanks.

example of setting the default value: (Swift 3)

if (UserDefaults.standard.value(forKey: "highScoreLife") == nil) { highScoreLife = 0 UserDefaults.standard.set(highScoreLife, forKey: "highScoreLife") } else { highScoreLife = Int32(UserDefaults.standard.integer(forKey: "highScoreLife") as Int) }