Servos jittering, 2 servos 6 motors 1 power supply

I'm trying to run 2 servos and 6 motors off one power supply (1 servo 3 motors controlled each arduino).
However, I'm having trouble with the servos jittering.
I've tried adding a large capacitor across the power supply, which didnt fully solve the issues, and I tried adding a small capacitor across the control of the servos and ground, but that stopped them from working.
I've attached the code below in full, but I can explain components if required.
The motors are controlled by Mosfets, and the servos by buttons.

#include <LiquidCrystal_I2C.h>
#include <Wire.h>
#include <Servo.h>

Servo servo;

unsigned long rtime;

int paddlemotorControl = 8;
int turnmotorControl = 9;
int endmotorControl = 10;

unsigned long timer = 0;
unsigned long bolttimer = 0;

const byte buttonPin = 11;
byte buttonState = LOW;
byte lastButtonState = LOW;
boolean servoFlag = false;

const int buttonaddPin = 12;
int buttonaddState = 0;

int totalcounter = 0;
int tcounter = 0; //total bolts
int cinput = 0;
int coutput = 0;
int clive = 0;
int prevcinput = 0;
int cbatcher = 0;

int dclive = 0;
int dtcounter = 0;

int currentState = 0; //For the final light gate
int previousState = 0;
int currentState2 = 0; //For the initial light gate
int previousState2 = 0;

int sensorPin = A0; //For the final light gate
int sensorValue = 0; 
int sensorPin2 = A1; //For the initial light gate
int sensorValue2 = 0;

int load = 0;
int starter = 0;
int paddlestarter = 0;
int turnstarter = 0;
int var = 0;
int batch = 0;
boolean stopper = false;
int presenceState = 0;

int c1 = 0;
int c2 = 0;
int cs = 0;
int ps = 0;
int dps1 = 0;
int dps2 = 0;

LiquidCrystal_I2C lcd(0x27,20,4);

void setup() {
servo.attach(2);
pinMode(buttonPin, INPUT);
pinMode(buttonaddPin,INPUT);

pinMode(paddlemotorControl, OUTPUT);
pinMode(turnmotorControl, OUTPUT);
pinMode(endmotorControl, OUTPUT);
Serial.begin(9600);
servo.write(0);

  lcd.init();                      // initialize the lcd 
  lcd.init();

  lcd.backlight();

  
}
void loop(){
  
rtime = millis();  

tcounter = totalcounter - coutput;
clive = cinput - coutput;
  Serial.println("c");
  Serial.println(sensorValue);
  Serial.println(sensorValue2);
  Serial.println("t");
  Serial.println();
  Serial.println();
  Serial.println("s");
  Serial.println();
  Serial.println();
  
  if (stopper == false){
 Serial.println("Connected!");
}else{
 Serial.println("Failed!");}



if(starter == 0){  //ONE
    digitalWrite(endmotorControl, HIGH);
  }
  
if(paddlestarter == 0){
    digitalWrite(paddlemotorControl, HIGH);
  }
  
if(turnstarter == 0){
    digitalWrite(turnmotorControl, HIGH);
  }
  
  
  
  //total bolts =  tcounter, add button to add (10) to tcounter - like bc scanner.  counter2 = #live bolts
  
  lcd.setCursor(0,0); // TWO
  lcd.print("RGS Cash Guys");
  lcd.setCursor(0,1);
  lcd.print("Bolt Distribution"); 
   lcd.setCursor(0,2);
  lcd.print("Qashqai =");
  lcd.setCursor(4,3);
  lcd.print(" bolts are live");
  

  
  if(clive < 10){
    lcd.setCursor(0,3);
  lcd.print(clive);
    lcd.setCursor(1,3);
  lcd.print("  ");
  }
  
  if(clive >= 10){
    if(clive <= 100){
          lcd.setCursor(0,3);
  lcd.print(clive);
    lcd.setCursor(2,3);
  lcd.print("  ");    }}
  
      
  if(clive >= 100){
        lcd.setCursor(0,3);
  lcd.print(clive);
    lcd.setCursor(3,3);
  lcd.print("  ");}
    
  if(tcounter < 10){
        lcd.setCursor(10,2);
  lcd.print(tcounter);
    lcd.setCursor(11,2);
  lcd.print("  ");}
  
  if(tcounter >= 10){
    if(tcounter <= 100){
          lcd.setCursor(10,2);
  lcd.print(tcounter);
    lcd.setCursor(12,2);
  lcd.print("  ");    }}
      
  if(tcounter >= 100){
        lcd.setCursor(10,2);
  lcd.print(tcounter);
    lcd.setCursor(13,2);
  lcd.print("  ");  }

    
    
buttonState = digitalRead(buttonPin);
buttonaddState = digitalRead(buttonaddPin);

if(buttonaddState == HIGH){//to add bolts, count 10 and add, then press button to sync with counter system
    cs = 1; }else{
    cs = 0;
    ps = 0;}

if(cs != ps) {
    if(cs == 1){
      totalcounter = totalcounter + 10;  
      ps = 1;
    }}
      

  

sensorValue2 = analogRead(sensorPin2); // read input value of 1st light gate 

if (sensorValue2 >= 900) { 
  currentState2 = 1;} else {
  currentState2 = 0;}
  
if(currentState2 != previousState2){
    if(currentState2 == 1){
    cinput = cinput + 1;}}
    
previousState2 = currentState2;

  
  sensorValue = analogRead(sensorPin); //read sensor value of 2nd light gate
  
if (sensorValue >= 000) { 
    currentState = 1;} else {
    currentState = 0;}
    
  if(currentState != previousState){
    if(currentState == 1){
  coutput = coutput + 1;}}

previousState = currentState;





if(cinput != prevcinput){  // THREE 
    paddlestarter = 1;
    digitalWrite(paddlemotorControl, LOW);
    stopper = true;
    }
    
prevcinput = cinput;
    
    
if(clive >= 8){ //FOUR
 
    turnstarter = 1;

     digitalWrite(turnmotorControl, LOW);}   
      
      
      
      



if(coutput - 4 == cbatcher){   ///FIVE

    starter = 1;
    digitalWrite(endmotorControl, LOW);
    batch = batch + 1;
    cbatcher = coutput;
    load = 1;
    }

if(load == 1){   //SIX
    if (servoFlag == false && lastButtonState != buttonState)
  {
    lastButtonState = buttonState;

    if (buttonState == HIGH)
    {
      servo.write(60);

      Serial.println("servo at 60");

      timer = rtime;
      servoFlag = true;
    }
  }}

  if (servoFlag == true && rtime - timer >= 7500)
  {
    servo.write(0);

    Serial.println("servo at 0");
    load = 0;
    starter = 0;
    servoFlag = false;
  }
  
if(batch >= 2){   //SEVEN
      turnstarter = 0;
      batch = 0;}
      


if((stopper == true) && (clive < 5)){   //EIGHT 
  presenceState = cinput; 
  stopper = false;
  bolttimer = rtime;} else if(clive >= 5){ 
  paddlestarter = 1;
  digitalWrite(paddlemotorControl, LOW);
  }
  
if(presenceState == cinput && bolttimer <= rtime - 5000){
  paddlestarter = 0;
  stopper = false;
  bolttimer = 0;
  presenceState = 0;
    } else { if(bolttimer <= rtime - 5000){
      bolttimer = 0;
    }}
  
}

What could be going wrong?
Thanks.

p.s. yeah there are probs a lot of unnecessary variables, but im shite at code lol

What could be going wrong?

Most likely, the power supply can't supply the required current.

Post a wiring diagram (not Fritzing) and links to the motors and servos.