Switching between apps in Android causes Unity Player to start over and drops any network connections to server

Hello,

I've got a strange behaviour of the UnityPlayer on Android. Sometimes the app runs in background correctly sometimes not. E.g. when user want to rate my app and opened Play Market and then returned back to game either with 'back' button or thru the list of running apps the game is started again instead of continue from the previous state. I am using Unity 5.5.03f. I've changed in manifest file main activity name from default UnityPlayerActivity to previous used UnityPlayerNativeActivity but I've got the same unpredictable behaviour. Does the UnityPlayer saves its state or I should handle it by myself. If so then what should I do?

Thanks in advance!