+1.
These are not Water proof or even water resistant. Nothing about RC's are. Water can affect the ESC, motors, The Reciever, and absolutely any Servo. I don't care what they say, WP or WR. Been there. Not to say many don't run in the wet. Just need to be prepared for all types of water/moisture caused issues. Including your servo.
Take out the servo and see if it works properly while not connected to anything.