Details on the tractor? Model, year, etc.
On my B2650 there were two things contributing to creep: The follower bearing that rides in the neutral detent (at top of picture) and the neutral switch plunger (bottom left). Both were dragging and keeping the pedal from returning completely to the neutral position. Cleaning and lubing the bearing and replacing the switch fixed things up.
That view is from above through a panel removed from the floor of the cab. If you have an open station tractor, you might have to go underneath and look up on the right side below the treadle pedal.