[Smsteves]

Ho constatato che e' un problema della libreria di arduino.
Caricandone una diversa da gestore librerie le cose cambiano.

Prova questo codice

#define Neutral 1500 // -- minimum forward signal
#define Maxspeed 2000 // -- maximum forward signal
#define Antsx 1000 // -- in front servo signal sx
#define Antdx 2000 // -- in front servo signal dx
#define Postsx 1000 // out rear servo sx endpoint if inverted with postdx it reverse
#define Postdx 2000 //-- out rear servo dx endpoint if inverted with postsx it reverse
#define Center 0 //-- add or subtract xx value to center steering
#define Tolerance 1 //-- if poor quality servo vibrates try 5
#define Max_gain 950 //-- gain steering reduction by throttle if reverse add -
#define Slowlimit 1800 //-- slow forward without endpoint correction
#include <MobaTools.h>
MoToServo myservo;
unsigned int Rxpulse;
unsigned int Gaspulse ;
unsigned int Gain;
signed int NewPos, OldPos;
int  Stato;
int Stato_Led=0;
boolean Cmd_Led = false;
int Ledpin=13;
int Led=0;
int Tol_cont=0;
int Media_GAS=0;
int Media_RX=0;


void setup() {
  pinMode(7, INPUT); //-- throttle signal in pin
  pinMode(8, INPUT); //-- front servo signal in pin
  pinMode(Cmd_Led, OUTPUT);
  myservo.attach(10); //-- rear servo signal out pin
   myservo.setSpeed( 48 );
  Stato = 0;
 }

void loop() {
  if (Stato == 0) {
    //lettura
    Rxpulse = pulseIn(8, HIGH);   
    Gaspulse = pulseIn(7, HIGH);
    
  }
  if (Stato == 1) {
    //Calcolo
    if (Gaspulse > Slowlimit) {
      Gain = map(Gaspulse, Slowlimit, Maxspeed, 0, Max_gain );
      NewPos = map(Rxpulse, Antsx, Antdx, (Postsx + Gain), (Postdx - Gain));
      Led=1;
    }
    else {
      NewPos = map(Rxpulse, Antsx, Antdx, Postsx, Postdx);
      Led=2;
    }
  }
  if (Stato == 2) {
    //scrittura
    if (abs(NewPos - OldPos) > Tolerance) {
      myservo.write(NewPos + Center);
         OldPos=NewPos;
    }
  }
  // Incrementa stato per il prossimo loop
  ++Stato;
  // Incrementa tempo led per il prossimo loop
  ++Stato_Led;
  if (Stato == 3) {
    // riparte da 0
    Stato = 0;
  }  
  //ritardo esecuzione cicli/stati
  delay(1);
  if (Led == 1) {
    //led veloce
    if (Stato_Led>20) {
    Cmd_Led= !Cmd_Led;
      Stato_Led=0;
    }
    digitalWrite(Ledpin, Cmd_Led);
  }
  if (Led == 2) {
    //led lento
    if (Stato_Led>60) {
    Cmd_Led= !Cmd_Led;
      Stato_Led=0;
    }
    digitalWrite(Ledpin, Cmd_Led);
  } 
}

Tolerance e' a 1, prova solo a modificare la linea

myservo.setSpeed( 48 );

variando il numero 48 tra 1 e 256

La libreria si chiama MobaTools e credo che sia questa la soluzione