Had this issues before a long time ago with cheap servo. I found a site here and it was similar what i had and fixed. It was a setup issues, but hope its not a mechanical issues. If thats the case you will need to buy a new one. That happen to me when i 1st got into rc I tried to be cheap fixing and buying parts. End up spending alot of money more then buying a stronger servo with metal gears. If i were you I would either buy Savox or Highest RC servo. Now both is about the same price but savox makes to much noise and glitching. Means you have to buy a glitch buster. I end up going with Highest RC very smooth, no glitch buster require and quite. Myself and other team drivers has slammed to the wall. Well the servo act like it was nothing. Still strong and quite.