trouble with "If'' and "Else if" along with Boolean

Send 3 bytes

  //Send over the Serial Data;
  port.write( PacketStart ); 
  port.write(y_left);
  port.write(y_right);
//  port.write(crab_l);
//  port.write(crab_r);
//  port.write(vert_up);
//  port.write(vert_dwn);

}

How many bytes are you reading ?

{
  while(Serial.available() < 1);
  if (Serial.read() == PacketStart)
  {
    while (Serial.available() < 4);
    
    leftSpeed = Serial.read();
    rightSpeed = Serial.read();
    crab_left = Serial.read();
    crab_right = Serial.read();