unity android crash report problem

Hi I am getting a lot of reports with this bug in play console, but from the devices I tested on, and on most devices seems to work fine. Any idea what can cause this will be appreciated, thanks:

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.gamma.stackpuzzle/com.unity3d.player.UnityPlayerNativeActivity}: java.lang.ClassNotFoundException: Didn't find class "com.unity3d.player.UnityPlayerNativeActivity" on path: /mnt/asec/com.gamma.stackpuzzle-1/pkg.apk at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2309) at android.app.ActivityThread.access$700(ActivityThread.java:157) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1289) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:176) at android.app.ActivityThread.main(ActivityThread.java:5317) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869) at dalvik.system.NativeStart.main(Native Method) Caused by: java.lang.ClassNotFoundException: Didn't find class "com.unity3d.player.UnityPlayerNativeActivity" on path: /mnt/asec/com.gamma.stackpuzzle-1/pkg.apk at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:65) at java.lang.ClassLoader.loadClass(ClassLoader.java:501) at java.lang.ClassLoader.loadClass(ClassLoader.java:461) at android.app.Instrumentation.newActivity(Instrumentation.java:1071) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2171) ... 11 more