Servo motor turns to max angle & initial angle when using serial

Projects Networking, Protocols, and Devices
81

When I use this code to read the sent values, I can see values which are wrong displayed in the LCD screen, I can't understand how did these values pass the different switch cases since they are wrong....
The updated value takes time to get updated, & before it does, numbers like 2304 2559 255 2313 are displayed... (updated sent value is 9)
here is the code :

#include<SCServo.h>
SCSCL   sc;
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2); // set the LCD address to 0x3F for a 16 chars and 2 line display
int save[4];
int Servo_=0;
int ndx = 0;
int foundValue = 0;
int cursor = 0;

void setup() {
  lcd.init();
  lcd.clear();
  lcd.backlight();      // Make sure backlight is on
  Serial.begin(9600);
  // Serial.println("<Arduino is ready>");
  //  Serial1.begin(1000000);
  // sc.pSerial = &Serial1;


}

void loop() {
  if (Serial.available() > 0) { //at least 4 bytes were received
    ndx++;
    byte rc;
    rc = Serial.read();

    //    cursor += lcd.print(sum); //<---should be 'rc' not 'foundvalue'!
    //    cursor += lcd.print(" ");
    lcd.clear();
    switch (ndx) {
      case 1:
        if (rc != 0xFF) --ndx; //reset index count if first 2 received bytes is NOT 0xFF
        if (ndx < 0) ndx = 0;
        break;

      case 2:
        if (rc != 0xFF ) --ndx;
        break;

      case 3:
        if (rc == 0xFF) {
          --ndx;
        }
        else {
          foundValue = rc;
          foundValue <<= 8;
          save[2] = rc;
        }
        break;

      case 4:
        save[3] = rc;
        foundValue |= rc;
        ndx = 0;
        int sum = save[2] * 256 + save[3];
        lcd.setCursor(0, 0);
        lcd.print(foundValue);
        break;
    }
  }
  delay(50);    //Wait for 1s
}```