OnControllerCollider hit called when moving away from a surface

I am making a game where the player aims and fires a spherical projectile which sticks to certain surfaces. I am using a Character Controller and I am using OnControllerColliderHit to register collisions.

It works correctly except when the projectile tries to launch from a ceiling. When I launch the projectile from the ceiling, the projectile moves slightly but then OnControllerColliderHit registers a collision and the projectile remains stuck to the surface.

The bug only occurs when the surface normal has a y value between -0.3 and -1.0. The closer the value is to -1.0, the more extreme the bug becomes. When the value is -0.3 the bug only occurs when the projectile is fired at certain angles, however, when the value is -1.0 the bug always occurs.

I did consider that it might be caused by using a sphere instead of a capsule, but the bug remains even when I use a capsule projectile. I also tried adjusting the skin width of the CharacterController, but this had no effect.

 void OnControllerColliderHit(ControllerColliderHit hit)
 {
     switch(hit.gameObject.tag)
     {
     case "Bouncy":
         Vector3 fU = Vector3.Dot(control.velocity.normalized, hit.normal) * hit.normal;
         Vector3 fW = control.velocity.normalized - fU;
         
         Vector3 vecDirection = fW - fU;
         vecDirection.Normalize();
             
         scrMove.resetOnBounce();
         scrMove.setMoveVar(vecDirection);
             
         StateMachine.requestChange(StateMachine.State.ACCELERATE);
         break;
         
     case "Sticky":
         StateMachine.requestChange(StateMachine.State.LAND);
         break;
     }
 }

}