Hi trying to help a friend of mine out with his phantom 4, when the props are on his drone and you turn all of them by hand they are all quite except for one which makes a sound almost like the motor is shot, but yet if you take the prop of and spin it it sounds the same as the other ones, you only notice it with the props on, he also has a problem when he tries to start the motors up sometimes when he pushes both sticks to the center sometimes they will fire up and sometimes theres nothing could this be bcause of the one motor....Im including 2 videos one spinning the motors with the props on and one spinning with the props off so you can see the difference...this has be baffled, Im assuming the motor needs replacing but still doesnt explain the intermittent problem trying to start the motors with the sticks, anyone have any ideas