Flickering LED when servo moves
If you are powering the arduino via usb try not to do that or plug it in to an usb 3.0 (and higher) port. The reason for this is that the servo draws a lot of power and the standard usb 2.0 with 0.5A can't handle the load and you got an voltage drop. And in that period of time the led goes off. usb 3.0 (and higher) can handle up to 1.5A so this souldn't be an error.