HEF4511 with multiple 7 Segment Displays

Other Hardware LEDs and Multiplexing
2 
byte Latch1 = 8;
byte Latch2 = 9;
byte LT = 16;
byte BCDbit0 = 12;
byte BCDbit1 = 13;
byte BCDbit2 = 14;
byte BCDbit3 = 15;

void setup() 
{                
  pinMode(Latch1, OUTPUT);   
  pinMode(Latch2, OUTPUT);   
  pinMode(10, OUTPUT);      // for ??
  pinMode(11, OUTPUT);      // for ?? 
  pinMode(BCDbit0, OUTPUT);     
  pinMode(BCDbit1, OUTPUT);   
  pinMode(BCDbit2, OUTPUT);   
  pinMode(BCDbit3, OUTPUT);   
  pinMode(16, OUTPUT);      // for ??
  digitalWrite(LT, HIGH);   // Lamp Test
  digitalWrite(Latch1, HIGH);
  digitalWrite(Latch2, HIGH);
}

void loop() 
{   
  //  1 2
  digitalWrite(BCDbit0, HIGH); //Binary LSB
  digitalWrite(BCDbit1, LOW); 
  digitalWrite(BCDbit2, LOW); 
  digitalWrite(BCDbit3, LOW); //Binary MSB
  digitalWrite(Latch1, LOW);
  delay(100);
  digitalWrite(Latch1, HIGH);
  
  digitalWrite(BCDbit0, LOW); //Binary LSB
  digitalWrite(BCDbit1, HIGH); 
  digitalWrite(BCDbit2, LOW); 
  digitalWrite(BCDbit3, LOW); //Binary MSB
  digitalWrite(Latch2, LOW); 
  delay(100);
  digitalWrite(Latch2, HIGH);
  
  delay(1000); 
  
  //  3 4
  digitalWrite(BCDbit0, HIGH); //Binary LSB
  digitalWrite(BCDbit1, HIGH); 
  digitalWrite(BCDbit2, LOW); 
  digitalWrite(BCDbit3, LOW); //Binary MSB
  digitalWrite(Latch1, LOW);
  delay(100);
  digitalWrite(Latch1, HIGH);
  
  digitalWrite(BCDbit0, LOW); //Binary LSB
  digitalWrite(BCDbit1, LOW); 
  digitalWrite(BCDbit2, HIGH); 
  digitalWrite(BCDbit3, LOW); //Binary MSB
  digitalWrite(Latch2, LOW); 
  delay(100);
  digitalWrite(Latch2, HIGH);  
  
  delay(1000);
}

What are you doing with 4511 pin_4? Pull-up to +V?