Arduino Uno, Problem with Serial1 without USB connected

Hello all,
i have a strange beaviour with serial1 on arduino uno.
I am not using serial (attached to USB) at all , unfortunately my serial1 communication using plainprotocol.lib
is not working without USB on df wirelass gamepad attached.

See code below:

#include <Arduino.h>
#include <PlainProtocol.h>
#include "OneButton.h"
#include <Arduino_FreeRTOS.h>

void TaskGreenLed( void *pvParameters );

// # Product name: Wireless Joystick v2.2 for Arduino
// # Product SKU : DFR0182
// # Code Version: 2.0

// # Description:
// # The sketch for using the gamepad and print the button state and the analog values of the gamepad
// # to computer screen using serial monitor


String Buttons[17] = {"J2","J1","","S2","S1","UP","LEFT","DOWN","RIGHT","1","4","2","3","RZ1","RZ2","LZ1","LZ2"};
String JoystickName[4] = {"RX","RY","LX","LY"};
// Buttons Nmes

int buttonState[17];
int joystickState[4];
int AnalogButton[2];

int inputCommand = 0;

#define shackMotorPin 2
#define UBRR1H true

PlainProtocol GamepadData(Serial1, 9600);

OneButton StartButton(3, true);
OneButton SelectButton(4, true);
OneButton UpButton(5, true);
OneButton LeftButton(6, true);
OneButton DownButton(7, true);
OneButton RightButton(8, true);
OneButton Button_1(9, true);
OneButton Button_4(10, true);
OneButton Button_2(11, true);
OneButton Button_3(12, true);
OneButton Button_RZ1(13, true);
OneButton Button_RZ2(14, true);
OneButton Button_LZ1(15, true);
OneButton Button_LZ2(16, true);



void TaskGreenLed(void *pvParameters)
{
pinMode(17, OUTPUT);
while(1)
{
digitalWrite(17, HIGH);
vTaskDelay( 200 / portTICK_PERIOD_MS );
digitalWrite(17, LOW);
vTaskDelay( 200 / portTICK_PERIOD_MS );
}
}


void InitIO()
{
for(int i = 0; i < 17; i++ )
pinMode(i, INPUT);
pinMode(shackMotorPin,OUTPUT);
digitalWrite(shackMotorPin,LOW); // Stop shacking of the gamepad
}

void DataUpdate()
{

for(int i = 2; i < 17; i++ ) buttonState = digitalRead(i);
buttonState[0] = analogRead(0);
buttonState[1] = analogRead(1);
for(int i = 0; i < 4; i++ ) joystickState = analogRead(i);
for(int i = 4; i < 6; i++ ) AnalogButton[i-4] = analogRead(i);

}



// Up Buttom
void UpButtonPressed()
{
GamepadData.write("UP",2000); //set the speed to 100
}

void UpButtonUnPressed()
{
GamepadData.write("UP",1000); //set the speed to 100
}



// Down Button
void DownButtonPressed()
{
GamepadData.write("DOWN",2000); //set the speed to 100
}

void DownButtonUnPressed()
{
GamepadData.write("DOWN",1000); //set the speed to 100
}

/*******************************BaseDrive**************************/
//Left - drive on

void LeftButtonPressed()
{
GamepadData.write("BaseDrive",2000); //set the speed to 100
}

//Left - drive off
void LeftButtonUnPressed()
{
GamepadData.write("BaseDrive",1500); //set the speed to 100
}

// Right - drive on
void RightButtonPressed()
{
GamepadData.write("BaseDrive",1000); //set the speed to 100
}

// Right - drive off
void RightButtonUnPressed()
{
GamepadData.write("BaseDrive",1500); //set the speed to 100
}

/****************BaseDrive - End **************************/

void setup()
{
xTaskCreate(TaskGreenLed ,"TaskGreenLed",128,NULL,1,NULL);
Serial1.begin(9600);
GamepadData.init();
InitIO();
UpButton.attachLongPressStart(UpButtonPressed);
UpButton.attachLongPressStop(UpButtonUnPressed);
UpButton.setPressTicks(10);

DownButton.attachLongPressStart(DownButtonPressed);
DownButton.attachLongPressStop(DownButtonUnPressed);
DownButton.setPressTicks(10);

LeftButton.attachLongPressStart(LeftButtonPressed);
LeftButton.attachLongPressStop(LeftButtonUnPressed);
LeftButton.setPressTicks(10);

RightButton.attachLongPressStart(RightButtonPressed);
RightButton.attachLongPressStop(RightButtonUnPressed);
RightButton.setPressTicks(10);


}

void loop()
{

UpButton.tick();
DownButton.tick();
LeftButton.tick();
RightButton.tick();
delay(100);

}

Wonder why there is a debencency between Hardare Serial1 and USB (Serial) ?!