Well I don't remember your configuration. But if you have a low computer or Mac the from cold and dark (well this will happend in all configurations) you will have a drop to the middle of the fps you hadd in cold and dark, once you switch on batery. But in low ones and some Macs maybe it will droped to <19. There is no ptoblem in tha. Move your point of view a little and it will refresh back to normal. The crj when switching on has a big impact in plugin calculation in just one frame. Bottle neck. Let time pass or force it moving the camera viewpoit to the sky. In future we will see if we can have a better startup! But for now it is totally no problem, because is easily fixed.