Arduino : Not receiving complete data over Bluetooth when serial printing is ena

I have written an android application that sends IR codes of different appliances to Arduino over Bluetooth (HC05). Below you can find my android code and data which is I am trying to send to arduino.

 String msg ="ir/11/550,450,500,1450,550,450,500,500,450,500,500,500,500,500,500,450,550,450,550,1400,550,450,550,400,550,1450,550,400,550,450,550,1400,550,1450,500,1450,500,1500,450,1500,500,500,500,450,550,450,550,450,500,450,550,450,550,400,550,450,550,450,550,400,550,450,550,450,550,400,550,450,500,500,500,500,450,500,550,450,550,450,500,450,550,450,550,450,500,450,550,450,550,450,500,450,550,450,550,400,550,450,550,450,/101\r";
            
            outStream.write(msg.getBytes());
            outStream.flush();
            msg="ir/-1/900,50,100,1000,850,50,50,850,50,100,1050,450,600,2850,1050,50,50,900,500,250,250,1000,250,250,250,200,100,900,250,250,450,950,100,200,700,50,100,850,250,250,450,1100,650,250,150,800,50,200,250,250,250,/52\r";      
            outStream.write(msg.getBytes());
            outStream.flush();

I am able to receive the data properly from Arduino If I comment Serail print after processing the end of each input from BLE. But when I enable the serial print I am only receiving partial data in Ardunio. The issue is mostly on Arduino side Below you can find my Arduino code

#include <SoftwareSerial.h>
    
    #define arduino_rx_pin 6  //  arduino_rx_pin 10 ------->   Bluetooth_tx_pin
    #define arduino_tx_pin 5  //  arduino_tx_pin 8 ------->   Bluetooth_rx_pin
    SoftwareSerial mySerial(arduino_rx_pin, arduino_tx_pin); // RX, TX
    char  B, buff[600]; // character and character string buffer
    int  buffCount = 0; // how many characters in the buffer
    int  buffCharLimit = 600; // maximum characters allowed
    
    void setup() {
      // put your setup code here, to run once:
      mySerial.begin(9600);         //Sets the data rate in bits per second (baud) for mySerial data transmission
      Serial.begin(9600);
    
    }
    
    void loop() {
      // put your main code here, to run repeatedly:
      if ( mySerial.available() )
      {
    
         B = mySerial.read();
            Serial.print(B);
            if ((B == '\r') || (B == '\n'))  { // EOL detected
                end_line_and_print();
            }
            else { 
                 buff[buffCount++] = B; // packing a byte into the MUMBO JUMBO buffer
               if (buffCount >= buffCharLimit) { // prevent buffer overflow
                  end_line_and_print();
                }
        
            }
        
      }
     
    }
     void end_line_and_print(void)  { // note that if you want to DO anything with your buffered input
      // this is the place where I print it out and say goodbye data
      buff[buffCount++] = 0; // C strings end with a terminating zero.
      Serial.println();
      Serial.println(buff);// If i enable this line I am only gettign partial data from BLE. 
      buffCount = 0; // start the next line
      memset(buff, 0, sizeof(buff));
     
    }

I am not sure how I can rectify this issue with my code. The suspect is Serial.println(buff) under end_line_and_print(void) function . if I comment on this line it works as expected. But i need to understand the behaviour why it’s happening and why my Arduino is not processing the complete output.
The output of the program with Serial.println(buff) uncommented

ir/11/550,450,500,1450,550,450,500,500,450,500,500,500,500,500,500,450,550,450,550,1400,550,450,550,400,550,1450,550,400,550,450,550,1400,550,1450,500,1450,500,1500,450,1500,500,500,500,450,550,450,550,450,500,450,550,450,550,400,550,450,550,450,550,400,550,450,550,450,550,400,550,450,500,500,500,500,450,500,550,450,550,450,500,450,550,450,550,450,500,450,550,450,550,450,500,450,550,450,550,400,550,450,550,450,/101
    ir/11/550,450,500,1450,550,450,500,500,450,500,500,500,500,500,500,450,550,450,550,1400,550,450,550,400,550,1450,550,400,550,450,550,1400,550,1450,500,1450,500,1500,450,1500,500,500,500,450,550,450,550,450,500,450,550,450,550,400,550,450,550,450,550,400,550,450,550,450,550,400,550,450,500,500,500,500,450,500,550,450,550,450,500,450,550,450,550,450,500,450,550,450,550,450,500,450,550,450,550,400,550,450,550,450,/101
    ir/-1/900,50,100,1000,850,50,50,850,50,100,1050,450,600,2850,10

You can clearly see the second input received only partially. I am not sure what is leading to this issue. I checked the free memory, It was till available.

The output of the program with Serial.println(buff) commented

ir/11/550,450,500,1450,550,450,500,500,450,500,500,500,500,500,500,450,550,450,550,1400,550,450,550,400,550,1450,550,400,550,450,550,1400,550,1450,500,1450,500,1500,450,1500,500,500,500,450,550,450,550,450,500,450,550,450,550,400,550,450,550,450,550,400,550,450,550,450,550,400,550,450,500,500,500,500,450,500,550,450,550,450,500,450,550,450,550,450,500,450,550,450,550,450,500,450,550,450,550,400,550,450,550,450,/101
    ir/-1/900,50,100,1000,850,50,50,850,50,100,1050,450,600,2850,1050,50,50,900,500,250,250,1000,250,250,250,200,100,900,250,250,450,950,100,200,700,50,100,850,250,250,450,1100,650,250,150,800,50,200,250,250,250,/52

The arduino has 64 byte buffers for Serial both in and out. When the input buffer is full, subsequent arriving characters are thrown away. When the output buffer is full, your code blocks until some characters have been transmitted to leave space.

I suspect that what is happening is that when you're printing that long string, the output buffer fills up, then the input buffer. While the print is waiting for space to put more characters in the buffer, incoming ones are being thrown away.

One possible solution would be to increase the baud rate (substantially) on Serial.

Thank you, that completely makes sense, But when I am increasing baud rate 115200 I am not seeing any data on the Arduino IDE serial monitor

You need to change the setting in the Serial monitor to match the baud rate you're using. Also, hopefully you left the baud rate for software serial unchanged.

Thank you very Much wildbill. That fixed my issues.