found the issue cause, its related to the resolution of the image i imported.
Images with to high resolution (like 1000 x 700) imported into sprite editor and resized inside the game layout cause this fps drops.
Depending the resolution it freezes the game for a time (fps 0-1) and after it unfreezes it works without any delay, including changing to left/right.
Also if you change the Browser tab when the game is freezed and go back, the object will be duplicated (including texts)
http://www.mediafire.com/?axuaacakaddeam4