Arduino Serial Printer Only Shows Partial Output on Button Press

I’m encountering a strange issue with my Arduino MIDI project and hoping someone can shed some light on it. I’m using an Arduino Uno, prototyping on a breadboard with hardware debounce circuits, and employing direct register programming with Pin Change Interrupts.

My code is designed to detect button presses using pin change interrupts. Specifically, when Button 2 (connected to pin D2) is pressed, the PCINT2_vect interrupt service routine is triggered. Inside this routine, I check if pin D2 was indeed the source using PIND & B00000100. Upon detection, I intend to print “B2_Pressed” to the Arduino Serial Printer for debugging. The code then enters a while loop to wait for the button release, after which it should print “B2_Released” to the arduino serial printer.

#include <MIDI.h>
#include <LibPrintf.h> //Used to print registers for debugging

MIDI_CREATE_DEFAULT_INSTANCE();

void setup() {
  //SECTION TO SET UP PORT REGISTERS FOR INPUT or OUTPUTS
  DDRD &= B00000011;   //Set D2-D7 (PD2-PD7) as an input using AND method.
  PORTD &= B00000011;  //Set D2-D7 (PD2-PD7) as LOW with AND method.
  DDRB &= B11000000;   //Set D8-D13 (PB0-PB5) as an Input using AND method.
  PORTB &= B11000000;  //Set D8-D13 (PB0-PB5) as LOW using AND method.

  MIDI.begin(MIDI_CHANNEL_OMNI); //Enable MIDI communication on all channels.
  Serial.begin(9600);         //SECTION TO SET UP PIN CHANGE INTERRUPTS ON ARDUINO UNO

  // Enable Pin Change Interrupt on Ports B, C and D.
  PCICR |= B00000111;  //Enable PCI for all Ports

  // Enable Port B, Pins PB0 thru PB5 (Digital Inputs D8-D13)
  PCMSK0 |= B00111111;

  // Enable Port C, Pins PC1 thru PC5 (Analog Inputs A1-A5)
  PCMSK1 |= B00111110;

  // Enable Port D, Pins PD2 thru PD7 (Digital Inputs D2-D7)
  PCMSK2 |= B11111100;
}

void loop() {
  //No code here. Interrupt driven program.
}

ISR (PCINT0_vect) // handle pin change interrupt for D8-D13 here
{
  Serial.println("Port B Interrupt Called");
  printf("PIND: %.8brn", PIND); //For DEBUG Only
}

ISR (PCINT2_vect) // handle pin change interrupt for D2 to D7 here. Use conditional statements to determine which exact pin was pressed.
{
  //Check if pin B2 (PD2) was triggered
  if(PIND & B00000100)
  {
    Serial.println("B2_Pressed");   //For DEBUG Only
    while (PIND & B00000100) {      //Wait here until B2 is released
    }
    Serial.println("B2_Released");  //For DEBUG Only
  }
  //Check if pin B3 (PD3) was triggered
  if(PIND & B00001000)
  {
    Serial.println("B3_Pressed");   //For DEBUG Only
    while (PIND & B00001000) {      //Wait here until B3 is released
    }
    Serial.println("B3_Released");  //For DEBUG Only
  }
}

The perplexing behavior I’m observing is that when I press Button 2, only the first two characters, ‘B2’, of “B2_Pressed” appear on the serial monitor. It’s not until I release the button that the remaining part of the first message, ‘_Pressed’, along with a carriage return, and then the entire “B2_Released” message are printed to the arduino serial printer.

Has anyone encountered a similar issue with the Arduino serial output being delayed or incomplete within interrupt routines, particularly when using a while loop for button debounce? Any insights into why the arduino serial printer is behaving this way and how to ensure the complete “B2_Pressed” message is printed immediately upon the button press would be greatly appreciated.