FrameRate problem in Samsung Galaxy S Advance

I have some problems testing on my Android device, the target framerate of my application is 60 FPS, it runs smoothly at that framerate, but sometimes the framerate drops to 20-25 and stays at that framerate.
This happens when i:

  • Put to sleep the phone
  • Go to home then i re-enter the application
  • Sometimes simply opening the game

It does not happens everytime, but when it happens i have to close completely the app (from task manager) and open it again to return to 60 FPS, any idea why is this happening?

Edit: im using Android 2.3.6

Edit 2: tried exporting a empty scene with only a FPS counter in it and it has the same problem

Edit 3: i discovered how to return to 60 fps when the game gets slower, if i press the sleep button twice quickly it goes black and then comes to the app again but now at the correct framerate, this is so strange, i hope there is a way to avoid it completely

I’m getting the same problem here.
Does anyone know how to avoid it?