I haven't used my drone for a few weeks now. I wanted to see if it still had some charge. The controller is switching on, but when trying to switch on the drone, 3 lights would light up, then go away, or if holding down would stay on until letting go of the button, but the drone wouldn't switch on. Given it a bit of charge as I thought this might be an issue. When trying to switch on the first 3 lights come on and the 4th flashes, but the drone still doesn't switch on. Is this normal behavior?