Problem with reading multiple potentiometer values on Arduino Uno
One problem is that if the value for pot1 has not changed, the value for pot2 will never be sent, even if it has changed, due to the early return when checking the value of pot1. You could fix this by changing to:

void readAndSendPotentiometerDataIfChanged(void) {

  //Potentiometer One
  int newPotentiometerOneValue = analogRead(A0) / 10.2;   
  if (newPotentiometerOneValue != lastPotentiometerOneValue) {
      Serial.print("!pos1");
      Serial.print(newPotentiometerOneValue);
      Serial.print(";");
      lastPotentiometerOneValue = newPotentiometerOneValue;
  }

  //Potentiometer Two
  int newPotentiometerTwoValue = analogRead(A1) / 10.2; 
  if (newPotentiometerTwoValue != lastPotentiometerTwoValue) {
      Serial.print("!pos2");
      Serial.print(newPotentiometerTwoValue);
      Serial.print(";");
      lastPotentiometerTwoValue = newPotentiometerTwoValue;
  }
}