Wont stop

I have a john deere js 63 self propelled walk behind mower it works great but now when i disengage the bail handle mower keeps moving .I took off transmission cover and checked spring tension and it was good . The little metal arm that spring is hooked to moves to the right and rear wheels turn but when i let go of handle the metal arm does not go back to the left, when i took spring off of metal arm on transmission the arm then moved all the way back to the left. What do u think it is ?

John Deere Model JS63 Walk Behind Mower Parts check your traction control cable for adjustment or replacement.