Data missing by Android App crash

I've received bug reports about data missing from my users when android app crashed. Such a incident has never been occurred in ios version. and now I'm using PreviewLabs.PlayerPrefs for good performance to save a user data. Write Permission of Playersettings is Internal.

Does anyone knows the root cause or have a good tips to investigate it more? I'm really appreciate if you can share some hints to solve it.

Unity ver. 5.5.0f3